I have made a public void method in my MainActivity to switch to another layout but whenever I call this method, the app crashes.
logcat:
07-05 16:35:22.823 14683-14712/com.example.name.mygame I/OpenGLRenderer: Initialized EGL, version 1.4
[ 07-05 16:35:24.724 14683:14754 D/]
HostConnection::get() New Host Connection established 0xae4b2240, tid 14754
07-05 16:35:28.500 14683-14754/com.example.name.mygame I/System.out: gameOverUi called!
-------- beginning of crash
07-05 16:35:28.558 14683-14754/com.example.name.mygame E/AndroidRuntime: FATAL EXCEPTION: Thread-218
Process: com.example.name.mygame, PID: 14683
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.Window.setContentView(int)' on a null object reference
at android.app.Activity.setContentView(Activity.java:2166)
at com.example.name.mygame.MainActivity.gameOverUi(MainActivity.java:15)
at com.example.name.mygame.GameView.gameOver(GameView.java:16)
at com.example.name.mygame.GameView.onDraw(GameView.java:188)
at com.example.name.mygame.GameLoopThread.run(GameLoopThread.java:37)
07-05 16:35:30.070 14683-14754/com.example.name.mygame I/Process: Sending signal. PID: 14683 SIG: 9
MainActivity:
package com.example.name.mygame;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new GameView(this));
}
public void gameOverUi(){
System.out.println("gameOverUi called!");
setContentView(R.layout.gameover); //Crash here
}
}
GameView class:
package com.example.name.mygame;
import android.content.Context;
import android.view.SurfaceView;
public class GameView extends SurfaceView {
MainActivity mActivity = new MainActivity();
public GameView(Context context) {
super(context);
//unimportant stuff
}
private void gameOver(){
mActivity.gameOverUi();
}
}
How can I change the content view without causing my application to crash? Any answers would be appreciated, thanks.
MainActivity mActivity = new MainActivity();
This is your problem.
This way you create a new allocation of a MainActivity, but you don't reference your MainActivity. For this, you have a null point exception.
Avoid this.
You are not referencing your MainActivity
class correctly within the GameView
- as you are currently creating a new object and not getting a reference to your Activity
that is being shown. This is not the correct way to access Activities.
As Activity
inherits from Context
you could theoretically do something like this:
public class GameView extends SurfaceView {
private MainActivity mActivity;
//Create new constructor to get the Activity
public GameView(Activity activity) {
super(activity);
mActivity = (MainActivity) activity;
}
private void gameOver(){
mActivity.gameOverUi();
}
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.