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App won't launch next activity and Crash

I want to press my Table Topics button to launch the Table Topics Activity and it ended up crashing the app but my code looks everything perfectly fine to me, I hope you guys can help me what's going on with my code. The Timing button used to work to launch other Activity but now I added the code for the Table Topics it just crash everything if I press any of the buttons
Here is my MainActivity.java
package com.iprex.light;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
public class MainActivity extends AppCompatActivity {
static MediaPlayer mp;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ActionBar actionBar = getSupportActionBar();
actionBar.hide();
setContentView(R.layout.activity_main);
}
public void onClickGreen(View view) {
startActivity(new Intent("com.iprex.green"));
}
public void onClickYellow(View view) {
startActivity(new Intent("com.iprex.yellow"));
}
public void onClickRed(View view) {
startActivity(new Intent("com.iprex.red"));
}
public void onClickTBTWhite(View view){
startActivity(new Intent("com.iprex.tbtwhite"));
}
}
This is my AndroidManifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.iprex.light">
<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>
<activity android:name=".Green" android:label="#string/app_name">
<intent-filter>
<action android:name="com.iprex.green"/>
</intent-filter>
</activity>
<activity android:name=".Yellow" android:label="#string/app_name">
<intent-filter>
<action android:name="com.iprex.yellow"/>
</intent-filter>
</activity>
<activity android:name=".Red" android:label="#string/app_name">
<intent-filter>
<action android:name="com.iprex.red"/>
</intent-filter>
</activity>
<activity android:name=".TBTWhite" android:label="Times">
<intent-filter>
<action android:name="com.iprex.tbtwhite"/>
</intent-filter>
</activity>
<activity android:name=".TBTGreen" android:label="Times">
<intent-filter>
<action android:name="com.iprex.tbtgreen"/>
</intent-filter>
</activity>
<activity android:name=".TBTYellow" android:label="Times">
<intent-filter>
<action android:name="com.iprex.tbtyellow"/>
</intent-filter>
</activity>
<activity android:name=".TBTRed" android:label="Times">
<intent-filter>
<action android:name="com.iprex.tbtred"/>
</intent-filter>
</activity>
</application>
</manifest>
This is the run log after I press the button
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.iprex.light, PID: 20558
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:6207)
at android.widget.TextView.performClick(TextView.java:11094)
at android.view.View$PerformClick.run(View.java:23639)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6688)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:6207) 
at android.widget.TextView.performClick(TextView.java:11094) 
at android.view.View$PerformClick.run(View.java:23639) 
at android.os.Handler.handleCallback(Handler.java:751) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6688) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358) 
Caused by: android.content.ActivityNotFoundException: No Activity found to handle Intent { act=com.iprex.tbtwhite launchParam=MultiScreenLaunchParams { mDisplayId=0 mFlags=0 } }
at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1839)
at android.app.Instrumentation.execStartActivity(Instrumentation.java:1531)
at android.app.Activity.startActivityForResult(Activity.java:4389)
at android.support.v4.app.BaseFragmentActivityApi16.startActivityForResult(BaseFragmentActivityApi16.java:54)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:65)
at android.app.Activity.startActivityForResult(Activity.java:4348)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:711)
at android.app.Activity.startActivity(Activity.java:4672)
at android.app.Activity.startActivity(Activity.java:4640)
at com.iprex.light.MainActivity.onClickTBTWhite(MainActivity.java:40)
at java.lang.reflect.Method.invoke(Native Method) 
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
at android.view.View.performClick(View.java:6207) 
at android.widget.TextView.performClick(TextView.java:11094) 
at android.view.View$PerformClick.run(View.java:23639) 
at android.os.Handler.handleCallback(Handler.java:751) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6688) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358) 

Your code to start other activities is not correct. Change your code to
public void onClickGreen(View view) {
startActivity(new Intent(this, Green.class));
}
public void onClickYellow(View view) {
startActivity(new Intent(this, Yellow.class));
}
public void onClickRed(View view) {
startActivity(new Intent(this, Red.class));
}
public void onClickTBTWhite(View view){
startActivity(new Intent(this, TBTWhite.class));
}
If you want to start other activities with package name and class name. Then you can try
public void onClickGreen(View view) {
openActivity("com.iprex.green", "com.iprex.green.Green");
}
public void onClickYellow(View view) {
openActivity("com.iprex.yellow", "com.iprex.yellow.Yellow");
}
public void onClickRed(View view) {
openActivity("com.iprex.red", "com.iprex.red.Green");
}
public void onClickTBTWhite(View view){
openActivity("com.iprex.tbtwhiten", "com.iprex.tbtwhite.TBTWhite");
}
private void openActivity(String packageName, String className) {
Intent intent = new Intent();
intent.setClassName(packageName, className);
startActivity(intent);
}
You can apply above code to other activities
Happy coding!

My app crashes when execute Intent statement [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I learn android studio programing and I have problem in my programs,
when I want to go to new activity using intent statement my app crashed,
this is my main activity;
public class MainActivity extends AppCompatActivity {
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAuth = FirebaseAuth.getInstance();
}
public void onStart(){
super.onStart();
FirebaseUser CurrentUser = mAuth.getCurrentUser();
if(CurrentUser == null){
Intent StartIntent = new Intent(MainActivity.this,
StartActivity.class);
startActivity(StartIntent);
finish();
}
}
}
and this is manifest :
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".MainActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".StartActivity"
android:label="#string/app_name">
</activity>
there is no error message
but thit is what i have into android monitor :
08-23 21:50:33.507 11264-11264/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.ruse.ayse.areyousmartenough, PID: 11264
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ruse.ayse.areyousmartenough/com.ruse.ayse.areyousmartenough.StartActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2378)
at android.app.ActivityThread.access$800(ActivityThread.java:155)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5433)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.ruse.ayse.areyousmartenough.StartActivity.onCreate(StartActivity.java:31)
at android.app.Activity.performCreate(Activity.java:5301)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2291)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2378) 
at android.app.ActivityThread.access$800(ActivityThread.java:155) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:136) 
at android.app.ActivityThread.main(ActivityThread.java:5433) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084) 
at dalvik.system.NativeStart.main(Native Method) 
I solved this problem into another project by adding "intent-filter" into manifest file but it does not work with this project,
this is StartActivity :
public class StartActivity extends AppCompatActivity {
private Button mRegBtn ;
private Button mLoginBtn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
mRegBtn = (Button) findViewById(R.id.RegBtn);
mLoginBtn = (Button) findViewById(R.id.LoginBtn);
mRegBtn.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view) {
Intent createAccount = new Intent(StartActivity.this, RegisterActivity.class);
startActivity(createAccount);
}
});
mLoginBtn.setOnClickListener(new View.OnClickListener(){ /////this is line 31
#Override
public void onClick(View view) {
Intent loginAccount = new Intent(StartActivity.this, LoginActivity.class);
startActivity(loginAccount);
}
});
}}

Your problem is at StartActivity.java:31 you are trying to read from a null reference.
By your comment, you look to miss getting the mLoginBtn from your Layout=
mLoginBtn = (Button) findViewById(R.id.btn_login);

Changing activity crashes

My app crashes when I try to navigate to another activity. Why does that happen?
I'm able to start the other activity when I launch it at first so there's no problem in the CheckUsernameActivity.
public class CheckNumberActivity extends AppCompatActivity {
EditText phoneNumberEditText;
Button countryCodeButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_check_number);
Button button = (Button) findViewById(R.id.okButton);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
countryCodeButton = (Button) findViewById(R.id.countryCodeButton);
phoneNumberEditText = (EditText) findViewById(R.id.phoneNumberEditText);
Log.v("areaCode", countryCodeButton.getText().toString());
Log.v("phoneNumber", phoneNumberEditText.getText().toString());
Intent k = new Intent(CheckNumberActivity.this, CheckUsernameActivity.class);
startActivity(k);
}
});
}
}

Try This way. I think it will help you.
public class CheckNumberActivity extends AppCompatActivity {
EditText phoneNumberEditText;
Button countryCodeButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_check_number);
Button button = (Button) findViewById(R.id.okButton);
countryCodeButton = (Button) findViewById(R.id.countryCodeButton);
phoneNumberEditText = (EditText) findViewById(R.id.phoneNumberEditText);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Log.v("areaCode", countryCodeButton.getText().toString());
Log.v("phoneNumber", phoneNumberEditText.getText().toString());
Intent k = new Intent(CheckNumberActivity.this, CheckUsernameActivity.class);
startActivity(k);
}
});
}
}

I didn't have my new activity defined in my manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.dimsumdev.runk" >
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme" >
<activity android:name=".activity.CheckNumberActivity" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".activity.CheckUsernameActivity" >
<!--Default Intent Filter-->
<intent-filter>
<action android:name="android.intent.action.DEFAULT" />
</intent-filter>
</activity>
<activity android:name=".activity.HomeActivity" >
</activity>
</application>
</manifest>

Unable to start an activity on button click

I have a button on main activity which onclick is supposed to start a activity
MainActivity.java
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void onButtonClick(View v){
if(v.getId()==R.id.lbutton)
{
Intent i = new Intent(MainActivity.this,Display.class);
startActivity(i);
}
}
}
lbutton is the id of button
Display.java
public class Display extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.secondsc);
}
}
secondsc.xml is a layout file which contains content for the new activity
Manifest.xml
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
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>
<activity android:name=".Display">
<intent-filter>
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

remove intent-filter to DisplayActivity in your manifest file:
<intent-filter>
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
And register your clickListener button
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewById(R.id.lbutton).setOnClickLIstener(new OnClickLIstener (){
void onClick (View v) {
onButtonClick(v);
}
});
}

You need to add an event listener to the button. You can either implement the View.OnClickListener interface and implement the onClick method (good if you have multiple buttons that need listeners), or use an anonymous class:
btn.setOnClickListener(new View.OnClickListener() {
onClick (View v) {
}
}

Are you sure that the OnButtonClick is being executed? I recommend doing it this way:
Button lButton = (Button) findViewById(R.id.lButton);
lButton.setOnClickListener(new OnClickListener() {
onClick(View view) {
Intent i = new Intent(MainActivity.this,Display.class);
startActivity(i);
}
}
-Daniel

App Crashing when changing activity

My app crashes when changing activity Here is my code,
I was following a tutorial on youtube, Everything seems to be exactly like his code. See if you can help
Everything seems to be inorder, I copyed everything exactly,
Manifest:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.helloworld"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<application
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".Splash"
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>
<activity
android:name=".MainActivity"
android:label="#string/title_activity_main" >
<intent-filter>
<action android:name="com.example.helloworld.MAINACTIVITY" />
<category android:name="android.intent.category.DEFUALT" />
</intent-filter>
</activity>
</application>
</manifest>
MainActivity:
package com.example.helloworld;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.app.Activity;
public class MainActivity extends Activity {
int counter;
Button add, sub;
TextView display;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
counter = 0;
add = (Button) findViewById(R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
add.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
counter++;
display.setText("Your Total is " + counter);
}
});
sub.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
counter--;
display.setText("Your Total is " + counter);
}
});
}
}
Splash.java:
package com.example.helloworld;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
public class Splash extends Activity{
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.splash);
Thread timer = new Thread(){
public void run(){
try{
sleep(5000);
} catch (InterruptedException e){
e.printStackTrace();
}finally{
Intent openStartingPoint = new Intent("com.example.helloworld.MAINACTIVITY");
startActivity(openStartingPoint);
}
}
};
timer.start();
}
}
Logcat:
07-19 20:35:36.068: E/AndroidRuntime(1442): FATAL EXCEPTION: Thread-74
07-19 20:35:36.068: E/AndroidRuntime(1442): android.content.ActivityNotFoundException: No Activity found to handle Intent { act=com.example.helloworld.MAINACTIVITY }
07-19 20:35:36.068: E/AndroidRuntime(1442): at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1512)
07-19 20:35:36.068: E/AndroidRuntime(1442): at android.app.Instrumentation.execStartActivity(Instrumentation.java:1384)
07-19 20:35:36.068: E/AndroidRuntime(1442): at android.app.Activity.startActivityForResult(Activity.java:3190)
07-19 20:35:36.068: E/AndroidRuntime(1442): at android.app.Activity.startActivity(Activity.java:3297)
07-19 20:35:36.068: E/AndroidRuntime(1442): at com.example.helloworld.Splash$1.run(Splash.java:23)

Try changing:
Intent openStartingPoint = new Intent("com.example.helloworld.MAINACTIVITY");
To:
Intent openStartingPoint = new Intent(Splash.this, MainActivity.class);

I think the application crashes because you misspelled "DEFAULT" in the intent-filter.