Android lockCanvas()上的NullPointerException
我正在为Android开发一个小游戏(测试),但我不理解用SurfaceView制作一个好的计时器线程的逻辑 [SurfaceView object].getHolder().lockCanvas(null)有问题。问题是lockCanvas返回的值无效(在本例中为null) 我无法捕获此异常,因为我。。。不行/ 这是我的代码:Android lockCanvas()上的NullPointerException,android,nullpointerexception,Android,Nullpointerexception,我正在为Android开发一个小游戏(测试),但我不理解用SurfaceView制作一个好的计时器线程的逻辑 [SurfaceView object].getHolder().lockCanvas(null)有问题。问题是lockCanvas返回的值无效(在本例中为null) 我无法捕获此异常,因为我。。。不行/ 这是我的代码: package game; import game.logics.SceneGroup; import game.scenes.TeamScene; import j
package game;
import game.logics.SceneGroup;
import game.scenes.TeamScene;
import java.util.Timer;
import java.util.TimerTask;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.Window;
import android.view.WindowManager;
// Definição da Atividade
public class GameActivity extends Activity {
// Definição do Ambiente
public class GameSurface extends SurfaceView
implements SurfaceHolder.Callback {
public GameSurface(final Context context) {
super(context);
this.getHolder().addCallback(this);
this.setFocusable(true);
}
@Override
public void surfaceChanged(final SurfaceHolder arg0,
final int arg1, final int arg2, final int arg3) {}
@Override
public void surfaceCreated(final SurfaceHolder arg0) {
GameActivity.this.running = true;
}
@Override
public void surfaceDestroyed(final SurfaceHolder arg0) {
GameActivity.this.running = false;
}
public void update(final Canvas canvas) {
GameActivity.this.scenes.update(canvas);
}
}
class GameTask extends TimerTask {
@Override
public void run() {
if(GameActivity.this.running == false) {
return;
}
final SurfaceHolder holder =
GameActivity.this.surface.getHolder();
Canvas canvas = null;
try {
canvas = holder.lockCanvas();
canvas.drawColor(Color.BLACK);
synchronized(holder) {
GameActivity.this.surface.update(canvas);
}
}
finally {
if(canvas != null) {
holder.unlockCanvasAndPost(canvas);
}
}
}
}
private GameSurface surface;
private SceneGroup scenes;
private Timer timer;
private TimerTask task;
private boolean running = false;
@Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
this.getWindow().setFlags(
WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
// ### SOLVE: PROBLEM START HERE ###
this.surface = new GameSurface(this);
this.scenes = new SceneGroup(this);
this.scenes.add(new TeamScene(this));
this.timer = new Timer();
this.task = new GameTask();
// ### SOLVE: PROBLEM END HERE ###
// ### Invalid new instance of GameSurface ###
this.setContentView(new GameSurface(this));
}
@Override
public void onPause() {
super.onPause();
this.timer.cancel();
}
@Override
public void onResume() {
super.onResume();
this.timer.scheduleAtFixedRate(this.task, 0, 33);
}
}
我做得对吗?
如何修复我的代码?您正在创建两次游戏界面 一旦来到这里:
this.surface = new GameSurface(this);
在这里:
this.setContentView(new GameSurface(this));
大概它们应该是同一个?我怀疑您的问题在于您正在从非guid线程调用surface.getHolder()。将支架保存在onCreate方法中,然后访问lockCanvas,查看是否有帮助。谢谢。但是我已经试过了,比如
this.surface=newgamessurface(this);/*然后*/this.holder=this.surface.getHolder()代码>但太多不起作用。我的问题还有一个嫌疑犯吗?嗯。。。你知道你要创建两次游戏界面吗?一个是您分配给this.surface的,另一个是您传递给setContentView的。。。想必他们应该是同一个?!?你是一个和蔼可亲的鹰眼人!哈哈,我真是个笨蛋。我检查了所有东西,没有注意到这个简单的问题。非常感谢。我已经从你的问题中删除了感谢。并不是说我不欣赏它,只是不是它的工作方式:)很高兴你在前进。