Its been a while since I made an app. So I may be forgetting something. Whenever I press a button to start another intent, the app crashes. Is there something I'm missing?
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
Button playButton = findViewById(R.id.play_button);
playButton.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
Intent play = new Intent(MainActivity.this, PointsActivity.class);
startActivity(play);
}
});
Button leaderButton = findViewById(R.id.leader_board);
leaderButton.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
Intent leader = new Intent(MainActivity.this, LeaderBoard.class);
startActivity(leader);
}
});
}
}
Look like you are not declaring your next activity in AndroidMainfest.xml
<manifest ... >
<application ... >
<activity android:name=".PointsActivity" />
<activity android:name=".LeaderBoard" />
...
</application ... >
...
</manifest >
Without your stacktrace it is impossible to know what your error is, are you getting invalid casting exceptions? Usually you need to cast widgets into objects before assigning them to variables Ie your line
Button playButton = findViewById(R.id.playbutton);
should be
Button playButton = (Button)findViewById(R.id.playbutton);
notice the explicit cast to Button, you may be getting errors like cannot cast android.widget.button to button, this will fix those.
Related
I'm trying to start another activity by pressing on the cardview which has a friend finder id. But when I write home.java it gives me problems in the setOnClickListener. At homeActivity it tells me Cannot resolve method 'homeActivity' in 'HomeActivity'. because?
public class HomeActivity extends AppCompatActivity {
private CardView btn_home;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn_home = findViewById(androidx.appcompat.R.id.home);
btn_home.setOnClickListener(v -> homeActivity(new Intent(HomeActivity.this, TrovamicoActivity.class)));
}
btn_home.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(HomeActivity.this, TrovamicoActivity.class);
startActivity(intent);
}
});
If there is no code in the manifest, write it
<activity android:name=".TrovamicoActivity" />
My problem is the following.
my app has a 1 welcome screen where the user ckick the "continue" button and it goes to next screen. The next one contains a menu with several buttons.
my problem is that I can not open another activity on the second screen (on the first screen it opens normal)
more or less this scheme below
(| activity1> button continue | >> | activity2> button continue2 |> does not respond)
to compliment and test apk on a galaxy grand duos 4.2.2
code below
code 1 screen (welcome).
public class Main2Activity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
Button button7 = (Button) findViewById(R.id.button7);
button7.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
setContentView(R.layout.activity_main4);
}
});}}
code 2 tela
public class Main4Activity extends AppCompatActivity {
private Button prova;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main4);
prova = (Button) findViewById(R.id.button5);
prova.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent( Main4Activity.this, Main3Activity.class);
startActivity(intent);
}
});
}}
2 tela code xml button
<Button
android:id="#+id/button5"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_below="#+id/button4"
android:layout_marginTop="11dp"
android:text="tela 2"/>
First, I want to make sure that you understand what you are writing.
button7.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
setContentView(R.layout.activity_main4);
}
});
In your onclick, you only set your view of Main2Activity to screen of activity_main4.xml. But you are still standing in Main2Activity (It means you are in Main2Activity with view activity_main4.xml).
In this case, Main4Activity hasn't initialized and the button prova hasn't been initialized too. So when you press prova button, it won't do anything.
Second, to solve your problem, make Main4Activity be initialized, you must start it. So, instead of using:
setContentView(R.layout.activity_main4);
in Main2Activity, which only change the view, not the Activity. You should use
Intent intent = new Intent(Main2Activity.this, Main4Activity.class);
startActivity(intent);
Hope you can understand this!
Your problem is that you can't use setContentView(R.layout.activity_main4); to open another activity .You can use startActivity method to open another activity .
You can try this .
1.remove the code in your Main2Activity
setContentView(R.layout.activity_main4);
2.add change to this
button7.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent i=new Intent(Main2Activity.this,Main4Activity.this);
startActivity(i);
}
});}}
I've added a button to my activity XML file and I can't get it to open my other activity. Can some please tell me step by step on how to do this?
A. Make sure your other activity is declared in manifest:
<activity
android:name="MyOtherActivity"
android:label="#string/app_name">
</activity>
All activities must be declared in manifest, even if they do not have an intent filter assigned to them.
B. In your MainActivity do something like this:
Button btn = (Button)findViewById(R.id.open_activity_button);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, MyOtherActivity.class));
}
});
Using an OnClickListener
Inside your Activity instance's onCreate() method you need to first find your Button by it's id using findViewById() and then set an OnClickListener for your button and implement the onClick() method so that it starts your new Activity.
Button yourButton = (Button) findViewById(R.id.your_buttons_id);
yourButton.setOnClickListener(new OnClickListener(){
public void onClick(View v){
startActivity(new Intent(YourCurrentActivity.this, YourNewActivity.class));
}
});
This is probably most developers preferred method. However, there is a common alternative.
Using onClick in XML
Alternatively you can use the android:onClick="yourMethodName" to declare the method name in your Activity which is called when you click your Button, and then declare your method like so;
public void yourMethodName(View v){
startActivity(new Intent(YourCurrentActivity.this, YourNewActivity.class));
}
Also, don't forget to declare your new Activity in your manifest.xml. I hope this helps.
References;
Starting Another Activity (Official API Guide)
If you declared your button in the xml file similar to this:
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="next activity"
android:onClick="goToActivity2"
/>
then you can use it to change the activity by putting this at the java file:
public void goToActivity2 (View view){
Intent intent = new Intent (this, Main2Activity.class);
startActivity(intent);
}
Note that my second activity is called "Main2Activity"
Button T=(Button)findViewById(R.id.button_timer);
T.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent i=new Intent(getApplicationContext(),YOURACTIVITY.class);
startActivity(i);
}
});
Write code on xml file.
<Button android:width="wrap_content"
android:height="wrap_content"
android:id="#+id/button"
android:text="Click"/>
Write Code in your java file
Button button=(Button)findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
startActivity(new Intent(getApplicationContext(),Secondclass.class));
/* if you want to finish the first activity then just call
finish(); */
}
});
use the following code to have a button, in android studio, open an already existing activity.
Button StartButton = (Button) findViewById(R.id.YOUR BUTTONS ID GOES HERE);
StartButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, YOUR ACTIVITY'S ID GOES HERE.class));
}
});
I did the same that user9876226 answered.
The only differemce is, that I don't usually use the onClickListener. Instead I write following in the xml-file: android:onClick="open"
open is the function, that is bound to the button.
Then just create the function open() in your activity class. When you click on the button, this function will be called :)
Also, I think this way is more confortable than using the listener.
Apply the following steps:
insert new layout xml in folder layout
rename window2
add new button and add this line: android:onClick="window2"
mainactivity.java
public void openWindow2(View v) {
//call window2
setContentView(R.layout.window2);
}
}
Use following steps to add the new activity (Manifest file will be automatically update)
File > New > Activity > Empty Activity
In your MainActivity.java file add the following code inside protected void onCreate(Bundle savedInstanceState).
Make sure you call finish(); function at the end. So when you tap the Back button, it will not go back to the previous activity.
Button btn = (Button)findViewById(R.id.open_activity_button);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, MyOtherActivity.class));
finish();
}
});
i keep getting thrown a NullPointer Exception in Android 4.1 while switching between Activities. Any thoughts on why?
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_launch);
Button login = (Button)findViewById(R.id.login_button);
Button join = (Button)findViewById(R.id.join_button);
login.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Intent i = new Intent(LaunchActivity.this, LoginActivity.class);
startActivity(i);
}});//END OF CLICK
join.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Intent i = new Intent(LaunchActivity.this, JoinActivity.class);
startActivity(i);
}});//END OF CLICK
}
From your question description i am assuming that you are getting this error because, you haven't add LoginActivity & JoinActivity both these activity into your AndroidManifest.xml. Just add them into AndroidManifest.xml as follows,
<activity android:name=".LoginActivity"></activity>
<activity android:name=".JoinActivity"></activity>
public class SuperActivity extends Activity{
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button registerButton = (Button) findViewById(R.id.register_button);
registerButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent myIntent = new Intent(SuperActivity.this, Register.class);
startActivity(myIntent);
}
});
Button loginButton = (Button) findViewById(R.id.login_button);
loginButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent myIntent = new Intent(SuperActivity.this, Login.class);
startActivity(myIntent);
}
});
}
}
My register buttons works but not the login button. Is something wrong with my code?
The code posted looks fine. What exactly doesn't work? Do you get an error?
Since you mention it works for 'register' but not for 'login', you may want to double check if you didn't forget to add Login to your manifest.
Is button with id login_button declared in main layout? If I had to guess this button is not declared in main layout is declared somewhere else.
double check if button with id login_button declared in main layout
Since you are not posting your logcat view,it's very difficult to see where the problem this.I'm suggesting you few things which you should make sure that are inplace as said by me.If not then please correct them and let me know if that solved your problem or not.
Firstly,you should make sure that you have declared a button with same id in your main.xml file.It will look something like this:
<button android:id="#+id/login_button" >
</button>
Secondly you should make sure that you have declared your Login.class in your AndroidManifest.xml file.It will look something like this:
<application>
<activity android:name=".Login"></activity>
</application>
Check if these things are in place or not.
Have you declared all the activities? ;)