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Moving from activity A to activity B and back from activity B to activity A

I'm very new to this and I've been looking around the forum for a while to get an answer to my question but I can't seem to get this working and I would very much appreciate help from your pros :)
As the title specifies I would like to go from activity A to activity B on a button click and from activity B on a button click go back to activity A.
My problem is first of all that I can't even go from activity A to activity B because the app crashes when I press the button. Why?
Second I would like to know if my code for returning from activity B to activity A is correct.
My code to go from activity A to activity B
public Button button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void ToCV(View v) {
Intent intent = new Intent(this, CV.class);
startActivity(intent);
}
}
And now the code for returning from Activity B to Activity A
public class CV extends AppCompatActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cv);
}
public void GoBack(View v) {
startActivity(new Intent(CV.this,MainActivity.class));
}
}
here is the crash log when i run the app##
2021-03-03 11:29:46.290 4104-4104/com.example.cvapp D/AndroidRuntime: Shutting down VM
2021-03-03 11:29:46.291 4104-4104/com.example.cvapp W/m.example.cvap: Accessing hidden method Lcom/msic/qarth/PatchStore;->createDisableExceptionQarthFile(Ljava/lang/Throwable;)Z (blacklist, JNI)
2021-03-03 11:29:46.291 4104-4104/com.example.cvapp E/m.example.cvap: [qarth_debug:] get PatchStore::createDisableExceptionQarthFile method fail.
2021-03-03 11:29:46.296 4104-4104/com.example.cvapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.cvapp, PID: 4104
java.lang.IllegalStateException: Could not execute method for android:onClick
at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:414)
at android.view.View.performClick(View.java:6659)
at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:992)
at android.view.View.performClickInternal(View.java:6631)
at android.view.View.access$3100(View.java:790)
at android.view.View$PerformClick.run(View.java:26187)
at android.os.Handler.handleCallback(Handler.java:907)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:216)
at android.app.ActivityThread.main(ActivityThread.java:7625)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409)
at android.view.View.performClick(View.java:6659) 
at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:992) 
at android.view.View.performClickInternal(View.java:6631) 
at android.view.View.access$3100(View.java:790) 
at android.view.View$PerformClick.run(View.java:26187) 
at android.os.Handler.handleCallback(Handler.java:907) 
at android.os.Handler.dispatchMessage(Handler.java:105) 
at android.os.Looper.loop(Looper.java:216) 
at android.app.ActivityThread.main(ActivityThread.java:7625) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987) 
Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.cvapp/com.example.cvapp.CV}; have you declared this activity in your AndroidManifest.xml?
at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:2112)
at android.app.Instrumentation.execStartActivity(Instrumentation.java:1757)
at android.app.Activity.startActivityForResult(Activity.java:4803)
at androidx.fragment.app.FragmentActivity.startActivityForResult(FragmentActivity.java:676)
at android.app.Activity.startActivityForResult(Activity.java:4743)
at androidx.fragment.app.FragmentActivity.startActivityForResult(FragmentActivity.java:663)
at android.app.Activity.startActivity(Activity.java:5164)
at android.app.Activity.startActivity(Activity.java:5132)
at com.example.cvapp.MainActivity.ToCV(MainActivity.java:21)
at java.lang.reflect.Method.invoke(Native Method) 
at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:409) 
at android.view.View.performClick(View.java:6659) 
at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:992) 
at android.view.View.performClickInternal(View.java:6631) 
at android.view.View.access$3100(View.java:790) 
at android.view.View$PerformClick.run(View.java:26187) 
at android.os.Handler.handleCallback(Handler.java:907) 
at android.os.Handler.dispatchMessage(Handler.java:105) 
at android.os.Looper.loop(Looper.java:216) 
at android.app.ActivityThread.main(ActivityThread.java:7625) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987) 
The manifest
`<?xml version="1.0" encoding="utf-8"?>
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/Theme.CVapp">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

Register your Activity B in the manifest file

Put these lines in your maifest
<activity android:name=".CV"/>

You should register Activity B in your AndroidManifest.xml
Your manifest should look like this:
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/Theme.CVapp">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".CV"/>
</application>
And also if you want to return from Activity B to Activity A, you can call method ->
finish() - in Activity B and that will destroy Activity B and return to previous activity and that's Activity A.

Null pointer exception on 'android.content.Context.getApplicationInfo()' [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 2 years ago.
I'm very new to android, just took it as a weekend development for fun, trying to make a very simple app and I'm having an error.
AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.gwallet">
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
MainActivity.java:
public class MainActivity extends AppCompatActivity {
Context context;
final TextView txtNewDailyDetailDescription = findViewById(R.id.txt_new_daily_detail_description);
final TextView txtNewDailyDetailSpend = findViewById(R.id.txt_new_daily_detail_spend);
final Button btnNewDailyDetail = findViewById(R.id.btn_new_daily_detail);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = this;
txtNewDailyDetailSpend.setInputType(InputType.TYPE_CLASS_NUMBER);
btnNewDailyDetail.setOnClickListener(new View.OnClickListener(){
public void onClick(View v) {
btnNewDailyDetailClick();
}
});
}
protected void btnNewDailyDetailClick() {
//Some irrelevant code.
}
}
Stack trace of the error:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.gwallet, PID: 32507
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.gwallet/com.gwallet.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3027)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3264)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1955)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7091)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:164)
at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:157)
at android.content.Context.obtainStyledAttributes(Context.java:677)
at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:692)
at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:659)
at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:479)
at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:214)
at com.gwallet.MainActivity.<init>(MainActivity.java:18)
at java.lang.Class.newInstance(Native Method)
at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:69)
at androidx.core.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:41)
at android.app.Instrumentation.newActivity(Instrumentation.java:1219)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3015)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3264) 
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1955) 
at android.os.Handler.dispatchMessage(Handler.java:106) 
at android.os.Looper.loop(Looper.java:214) 
at android.app.ActivityThread.main(ActivityThread.java:7091) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975) 
I do get that something that is not initialized is being tried to get in use, but I don't know what it is. I keep reading Activities documentation. Any help?

Let me know if this work!
public class MainActivity extends AppCompatActivity {
Context context;
TextView txtNewDailyDetailDescription;
TextView txtNewDailyDetailSpen;
Button button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
txtNewDailyDetailDescription=findViewById(R.id.txt_new_daily_detail_description);
txtNewDailyDetailSpend = findViewById(R.id.txt_new_daily_detail_spend);
btnNewDailyDetail = findViewById(R.id.btn_new_daily_detail);
context = this;
txtNewDailyDetailSpend.setInputType(InputType.TYPE_CLASS_NUMBER);
btnNewDailyDetail.setOnClickListener(new View.OnClickListener(){
public void onClick(View v) {
btnNewDailyDetailClick();
}
});
}
protected void btnNewDailyDetailClick() {
//Some irrelevant code.
}
}

Get String[] from the other class

This is my main class:
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
Context con;
protected void onClickCityBreak(View v) {
String [] arrayCityBreak = con.getResources().getStringArray(R.array.citybreak);
Intent myintent = new Intent(MainActivity.this, ActivityTo.class);
myintent.putExtra("PLACES",arrayCityBreak);
startActivity(myintent);
}
}
And this is the class i want to send myintent array to:
public class ActivityTo extends ListActivity {
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
String[] arrayCityBreak = getIntent().getStringArrayExtra("PLACES");
ArrayAdapter<String> adapterCityBreak = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayCityBreak);
ListView myview = getListView();
myview.setAdapter(adapterCityBreak);
}
}
My AndroidManifest.xml file:
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".ActivityTo">
</activity>
I can't find the problem in this. My application shuts down when i click the button to get to the new intent. It is because of the String[] i try to send, but I don't see why is won't work.
--------- beginning of crash
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.ivarrreyna.assignment, PID: 2626
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5198) 
at android.view.View$PerformClick.run(View.java:21147) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
at com.ivarrreyna.assignment.MainActivity.onClickCityBreak(MainActivity.java:24)
at java.lang.reflect.Method.invoke(Native Method) 
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
at android.view.View.performClick(View.java:5198) 
at android.view.View$PerformClick.run(View.java:21147) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
Application terminated.

There is no need to pass array to , since ActivityTo is also an activity so can fetch the resources array here too
public class ActivityTo extends ListActivity {
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
String [] arrayCityBreak = getResources().getStringArray(R.array.citybreak);
ArrayAdapter<String> adapterCityBreak = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayCityBreak);
ListView myview = getListView();
myview.setAdapter(adapterCityBreak);
}
}
To remove current error,
either do this
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
con=this;
}
or
use this in MainActivity because con is not initialized
String [] arrayCityBreak = getResources().getStringArray(R.array.citybreak);
instead of
String [] arrayCityBreak = con.getResources().getStringArray(R.array.citybreak);

My application shuts down when i click the button to get to the new intent. It is because of the String[] i try to send, but I don't see why is won't work.
It is caused by this con, because the context is null:
Context con;
Use this like:
String [] arrayCityBreak = this.getResources().getStringArray(R.array.citybreak);
or
String [] arrayCityBreak = getResources().getStringArray(R.array.citybreak);

Android app crashes on start with null pointer exception

I am new to android and java I tried to create a navigation drawer screen in android from the tutorials :
http://www.androidhive.info/2013/11/android-sliding-menu-using-navigation-drawer/
but I am getting exception as :
--------- beginning of crash
05-02 11:23:49.153 2738-2738/kanix.highrise.com.highrise E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: kanix.highrise.com.highrise, PID: 2738
java.lang.RuntimeException: Unable to start activity ComponentInfo{kanix.highrise.com.highrise/kanix.highrise.com.highrise.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
at android.app.Activity.performCreate(Activity.java:5937)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-02 11:23:49.390 2738-2751/kanix.highrise.com.highrise I/art﹕ Background partial concurrent mark sweep GC freed 360(66KB) AllocSpace objects, 0(0B) LOS objects, 52% free, 465KB/977KB, paused 1.273ms total 220.874ms
05-02 11:26:01.559 2791-2791/kanix.highrise.com.highrise D/AndroidRuntime﹕ Shutting down VM
05-02 11:26:01.715 2791-2791/kanix.highrise.com.highrise E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: kanix.highrise.com.highrise, PID: 2791
java.lang.RuntimeException: Unable to start activity ComponentInfo{kanix.highrise.com.highrise/kanix.highrise.com.highrise.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
at android.app.Activity.performCreate(Activity.java:5937)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-02 11:26:01.772 2791-2803/kanix.highrise.com.highrise I/art﹕ Background partial concurrent mark sweep GC freed 345(52KB) AllocSpace objects, 0(0B) LOS objects, 51% free, 479KB/991KB, paused 43.642ms total 205.582ms
05-02 11:27:33.452 2835-2835/kanix.highrise.com.highrise I/art﹕ Not late-enabling -Xcheck:jni (already on)
05-02 11:27:33.581 2835-2835/kanix.highrise.com.highrise D/AndroidRuntime﹕ Shutting down VM
05-02 11:27:33.581 2835-2835/kanix.highrise.com.highrise E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: kanix.highrise.com.highrise, PID: 2835
java.lang.RuntimeException: Unable to start activity ComponentInfo{kanix.highrise.com.highrise/kanix.highrise.com.highrise.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
at android.app.Activity.performCreate(Activity.java:5937)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-02 11:29:36.573 2917-2917/kanix.highrise.com.highrise D/AndroidRuntime﹕ Shutting down VM
05-02 11:29:36.573 2917-2917/kanix.highrise.com.highrise E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: kanix.highrise.com.highrise, PID: 2917
java.lang.RuntimeException: Unable to start activity ComponentInfo{kanix.highrise.com.highrise/kanix.highrise.com.highrise.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
at android.app.Activity.performCreate(Activity.java:5937)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
           
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
I copied the code and I had some activities in my code working perfectly but now I tried to add navigation drawer activity to my app but it crashes on start. My menifest file is like this:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="kanix.highrise.com.highrise" >
<application
android:allowBackup="true"
android:icon="#mipmap/icon"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".StartActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<action android:name="com.example.intentdemo.LAUNCH" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name=".LoginActivity"
android:icon="#mipmap/ic_launcher"
android:label="loginactivity" >
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<action android:name="com.example.intentdemo.LAUNCH" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="http" />
</intent-filter>
</activity>
<activity
android:name=".Dashboard"
android:label="#string/title_activity_dashboard" >
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<action android:name="com.example.intentdemo.LAUNCH" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name=".MainActivity"
android:label="#string/title_activity_main" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
My main activity java class is like this:
package kanix.highrise.com.highrise;
import java.util.ArrayList;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import kanix.highrise.com.highrise.adapter.NavDrawerListAdapter;
import kanix.highrise.com.highrise.model.NavDrawerItem;
public class MainActivity extends Activity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
// nav drawer title
private CharSequence mDrawerTitle;
// used to store app title
private CharSequence mTitle;
// slide menu items
private String[] navMenuTitles;
private TypedArray navMenuIcons;
private ArrayList<NavDrawerItem> navDrawerItems;
private NavDrawerListAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle = mDrawerTitle = getTitle();
// load slide menu items
navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);
// nav drawer icons from resources
navMenuIcons = getResources()
.obtainTypedArray(R.array.nav_drawer_icons);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.list_slidermenu);
navDrawerItems = new ArrayList<NavDrawerItem>();
// adding nav drawer items to array
// Home
navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
// Find People
navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
// Photos
navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
// Communities, Will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "22"));
// Pages
navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
// What's hot, We will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "50+"));
// Recycle the typed array
navMenuIcons.recycle();
mDrawerList.setOnItemClickListener(new SlideMenuClickListener());
// setting the nav drawer list adapter
adapter = new NavDrawerListAdapter(getApplicationContext(),
navDrawerItems);
mDrawerList.setAdapter(adapter);
// enabling action bar app icon and behaving it as toggle button
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, //nav menu toggle icon
R.string.app_name, // nav drawer open - description for accessibility
R.string.app_name // nav drawer close - description for accessibility
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
// calling onPrepareOptionsMenu() to show action bar icons
invalidateOptionsMenu();
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
// calling onPrepareOptionsMenu() to hide action bar icons
invalidateOptionsMenu();
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
// on first time display view for first nav item
displayView(0);
}
}
/**
* Slide menu item click listener
* */
private class SlideMenuClickListener implements
ListView.OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// display view for selected nav drawer item
displayView(position);
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// toggle nav drawer on selecting action bar app icon/title
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action bar actions click
switch (item.getItemId()) {
case R.id.action_settings:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/* *
* Called when invalidateOptionsMenu() is triggered
*/
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
// if nav drawer is opened, hide the action items
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
/**
* Diplaying fragment view for selected nav drawer list item
* */
private void displayView(int position) {
// update the main content by replacing fragments
Fragment fragment = null;
switch (position) {
case 0:
fragment = new HomeFragment();
break;
case 1:
fragment = new FindPeopleFragment();
break;
case 2:
fragment = new PhotosFragment();
break;
case 3:
fragment = new CommunityFragment();
break;
case 4:
fragment = new PagesFragment();
break;
case 5:
fragment = new WhatsHotFragment();
break;
default:
break;
}
if (fragment != null) {
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.frame_container, fragment).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(navMenuTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
} else {
// error in creating fragment
Log.e("MainActivity", "Error in creating fragment");
}
}
#Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
/**
* When using the ActionBarDrawerToggle, you must call it during
* onPostCreate() and onConfigurationChanged()...
*/
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggls
mDrawerToggle.onConfigurationChanged(newConfig);
}
}

You probably need to use an Action bar theme for your activity. Check out the first part of this document. You can specify a theme for the activity in the manifest in both the application and activity sections. For instance:
android:theme="#style/Theme.AppCompat.Light"

The major reason why app is crashing is you are using support Action bar toggle with Action Bar.
Try this convert your Activity to ActionBarActivity and use SupportActionBar in place of Action bar. ALso do not forget to use AppCompact theme with this in your style.xml.

Your code have error on Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
Check this link for to fixed the bugs.

Error associated with receiving parse.com push notification Android

I have been trying to implement parse.com push notifications on my iOS and android app. Ive successfully been able to implement this on iOS, however, I'm still struggling with the Android implementation. When the notification is received by the user, and the user presses the notification, i want to open up my 'HomeScreen' activity, and display the text from the notification in an alert Dialogue. the Receiver handler and manifest files are shown below, along with the LogCat. What am i doing wrong, and how do i fix it?
HomeScreen Java:
public class Receiver extends ParsePushBroadcastReceiver {
public Receiver(){
}
private static final String TAG = "MyNotificationsReceiver";
#Override
public void onPushOpen(Context context, Intent intent) {
Log.e("Push", "Clicked");
Intent i = new Intent(context, HomeScreen.class);
i.putExtras(intent.getExtras());
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(i);
try {
JSONObject json = new JSONObject(intent.getExtras().getString("com.parse.Data"));
String notificationText = json.getString("alert");
AlertDialog Alert= new AlertDialog.Builder(context)
.setTitle("News")
.setMessage(notificationText)
.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
}
})
.show();
} catch (JSONException e) {
Log.d(TAG, "JSONException: " + e.getMessage());
}
}
}
Manifest:
<service android:name="com.parse.PushService" />
<receiver android:name="com.parse.ParseBroadcastReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
<action android:name="android.intent.action.USER_PRESENT" />
</intent-filter>
</receiver>
<receiver android:name="com.parse.GcmBroadcastReceiver"
android:permission="com.google.android.c2dm.permission.SEND">
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
<action android:name="com.google.android.c2dm.intent.REGISTRATION" />
<!--
IMPORTANT: Change "com.parse.tutorials.pushnotifications" to match your app's package name.
-->
<category android:name="au.gov.nsw.shellharbour.saferroadsshellharbour" />
</intent-filter>
</receiver>
<receiver android:name="au.gov.nsw.shellharbour.saferroadsshellharbour.HomeScreen$Receiver" android:exported="false">
<intent-filter>
<action android:name="com.parse.push.intent.RECEIVE" />
<action android:name="com.parse.push.intent.DELETE" />
<action android:name="com.parse.push.intent.OPEN" />
</intent-filter>
</receiver>
Logcat:
java.lang.RuntimeException: Unable to instantiate receiver au.gov.nsw.shellharbour.saferroadsshellharbour.HomeScreen$Receiver: java.lang.InstantiationException: can't instantiate class au.gov.nsw.shellharbour.saferroadsshellharbour.HomeScreen$Receiver; no empty constructor
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2265)
at android.app.ActivityThread.access$1600(ActivityThread.java:143)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4963)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.InstantiationException: can't instantiate class au.gov.nsw.shellharbour.saferroadsshellharbour.HomeScreen$Receiver; no empty constructor
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1319)
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2260)
            at android.app.ActivityThread.access$1600(ActivityThread.java:143)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4963)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
            at dalvik.system.NativeStart.main(Native Method)

EDIT: Since Receiver is an inner class, it cannot exist outside of an instance of its outer class. This is why you cannot instantiate it via the manifest definition. To solve, mark Receiver as static, or define it as its own class file. (You can probably remove the empty constructor I had previously advised).
java.lang.InstantiationException: can't instantiate class au.gov.nsw.shellharbour.saferroadsshellharbour.HomeScreen$Receiver; no empty constructor
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2265)
You need a constructor so the receiver can be instantiated:
public Receiver(){
}