java - 膨胀 View

Question

我需要使用view.getWidth()，但我不能，因为我还没有膨胀 View 。在使用 view.getWidth() 之前如何膨胀 View ？

MainActivity 类:

        public class MainActivity extends Activity  {
    GameView gv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.game_view);
        LinearLayout surface = new LinearLayout(this);
        surface = (LinearLayout)findViewById(R.id.surface);
        gv= new GameView(this,surface);
        surface.addView(gv);
}

GameView 类:

       public class GameView extends SurfaceView implements Runnable {

        private boolean isRunning=false;
        private final long FPS=12;
        int PART_SIZE=6;

        private SurfaceHolder holder;
        Thread snakethread;
        Snake snake;
        Arena a;
        Brick food;
        LinearLayout view;
        Bitmap arena;

    public GameView(Context context,LinearLayout view) {
        super(context);
        this.view=view;
        arena = Bitmap.createBitmap(view.getWidth(), view.getHeight(),Bitmap.Config.ARGB_8888);
        this.a=new Arena();
        snakethread=new Thread(this);
        holder= getHolder();
        this.setBackgroundColor(Color.TRANSPARENT);                 
        this.setZOrderOnTop(true);
        getHolder().setFormat(PixelFormat.TRANSPARENT);

        holder.addCallback(new SurfaceHolder.Callback(){

            @Override
            public void surfaceCreated(SurfaceHolder arg0) {
                setRunning(true);
                snakethread.start();

            }

            @Override
            public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2,int arg3) {

            }

            @Override
            public void surfaceDestroyed(SurfaceHolder arg0) {

                setRunning(false);

                while(true){
                    try {
                        snakethread.join();
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
    });
        snake=new Snake(20, 50, "RIGHT",PART_SIZE);
}

    public void run() {
        long stepPerSecond=1000/FPS;
        long startTime;
        long sleepTime;
        Canvas c = null;
        try{
            c=this.getHolder().lockCanvas();
            synchronized (this.getHolder()) {
                ArenaDraw(c);
                }
        }
        catch(Exception e){
        }
        finally{
            if(c!=null){
                this.getHolder().unlockCanvasAndPost(c);
            }
        }
        while(isRunning){
            c=null;
            startTime=System.currentTimeMillis();
            try{
                c=this.getHolder().lockCanvas();
                synchronized (this.getHolder()) {
                    Paint p=new Paint();
                    snakeDraw(c);
                    }
            }
            catch(Exception e){
            }
            finally{
                if(c!=null){
                    this.getHolder().unlockCanvasAndPost(c);
                }
            }
            sleepTime= stepPerSecond-(System.currentTimeMillis()-startTime);
            if(sleepTime>0)
                try {
                    Thread.sleep(sleepTime);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
        }
    }

Answer 1

您可以使用ViewTreeObserver:

final ViewTreeObserver observer = surface.getViewTreeObserver();
observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
    public boolean onPreDraw() {
        observer.removeOnPreDrawListener(this);
        // do what you need to do, getWidth() is now valid
        surface.getWidth();
        return false; // will not draw this initial frame
    }
});

请注意，仅膨胀 View 是不够的。在 getWidth() 生效之前，您的 View 需要通过 inflate-measure-layout 生命周期。

了解更多关于how android draws views的信息.