Question

我有一个抓住touchEvents的surfaceview，然后在画布上绘制一个点。但是当我触摸时，SurfaceView会从红色变为黑色，而不是绘制一个点。请看一下我的代码：

GamemodeClassic.java

public class GamemodeClassic extends AppCompatActivity implements Runnable, View.OnTouchListener {

private SurfaceView view;

private GameClassic game;

@Override
protected void onCreate(Bundle savedInstanceState) {
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    super.onCreate(savedInstanceState);
    this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

    setContentView(R.layout.activity_gamemode_classic);

    init();
}

public void init() {
    view = (SurfaceView) findViewById(R.id.classic_view);
    game = new GameClassic(this);
    view.getHolder().addCallback(game);
    view.setOnTouchListener(game);
}

@Override
public void run() {

}

@Override
public boolean onTouch(View v, MotionEvent event) {
    return true;
}
}

GameClassic.java

public class GameClassic extends SurfaceView implements SurfaceHolder.Callback, View.OnTouchListener {

SurfaceHolder mainHolder;

public GameClassic(Context context) {
    super(context);

    setFocusable(true);
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
    mainHolder = holder;
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    initDraw(holder);
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {

}

public void initDraw(SurfaceHolder holder) {
    Canvas canvas = mainHolder.lockCanvas();
    if(canvas == null) {
        Log.v("testlog", "GameClassic.java - Canvas not available");
    }else{
        Log.v("testlog", "GameClassic.java - Canvas found, drawing");
        canvas.drawRGB(255, 0, 0);
    }

    holder.unlockCanvasAndPost(canvas);
}

public void drawPoint(float x, float y) {
    Canvas canvas = mainHolder.lockCanvas();

    if(canvas != null) {
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setColor(Color.BLUE);

        canvas.drawPoint(x, y, paint);

        mainHolder.unlockCanvasAndPost(canvas);
    }else{
        Log.v("testlog", canvas + "");
    }
}

@Override
public boolean onTouch(View v, MotionEvent event) {
    Log.v("testlog", event.getAction() + "sfsfsf");

    if(event.getAction() == MotionEvent.ACTION_DOWN) {
        drawPoint(event.getX(), event.getY());
        Log.v("testlog", "drawing point on (" + event.getX() + ";" + event.getY() + ")");
    }
    return true;
}
}

提前致谢

修改事实证明，我必须将行holder.unlockCanvasAndPost(canvas)更改为mainHolder.unlockCanvasAndPost(canvas)。仍然没有任何改进，但是当我尝试使用drawPoint中的canvas.drawRGB（）更改surfaceview的颜色时，它可以正常工作。然而，绘制点仍然会将表面视图变为黑色。

Answer 1

当您覆盖onTouch()时，您需要拨打super.onTouch()。可能是问题。

Answer 2

显然，当您锁定画布并在其上绘制时，整个画布将重置为其默认颜色，即黑色。当你在顶部画一个点时，蓝色几乎看不到，这让我觉得整个屏幕都变黑了。在该点之前重新绘制背景是解决方案。

Answer 3

在您的GameClassic构造函数中，将alpha设置为零。像这样：

public GameClassic (Context context) {
    super (context);

    setFocusable(true);

    setAlpha(0); // this is the secret
}

绘图时，SurfaceView会变黑

3 个答案: