画布SurfaceView

Question

我有自定义的SurfaceView，在onDraw方法中设置一个背景，然后绘制画布，但只看到背景。如何在背景上用画布作画？试图添加一个背景与画布，它工作，但在左上角2-3dp被删除，并重新绘制每次背景将占用大量的内存。那么它能用第一种方法还是第二种方法来完成吗?左上角没有空位吗？

编辑...

GameView.java

public class GameView extends SurfaceView {
    private Bitmap background;
    private SurfaceHolder holder;
    private GameManager gameLoopThread;

    public GameView(Context context, AttributeSet attrs) {
        super(context, attrs, 0);
        setWillNotDraw(false);
        gameLoopThread = new GameManager(this);
        holder = getHolder();
        holder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
                boolean retry = true;
                gameLoopThread.setRunning(false);
                while (retry) {
                    try {
                        gameLoopThread.join();
                        retry = false;
                    } catch (InterruptedException e) {
                    }
                }
            }

            @Override
            public void surfaceCreated(SurfaceHolder holder) {
                gameLoopThread.setRunning(true);
                gameLoopThread.start();
            }

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

        background = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
    }

    public void onDraw(Canvas canvas) {
        canvas.drawBitmap(background, 0, 0, null);
    }

    public void drawCanvas(Canvas canvas) {
        if (x < getWidth() - 10) {
            x += 10;
        } else {
            gameLoopThread.setRunning(false);
        }
        canvas.drawLine(0, 200, x, 200, paint);
    }
}

GameManager.java

public class GameManager extends Thread {
    private GameView view;
    private boolean running = false;

    public GameManager(GameView view) {
        this.view = view;
    }

    public void setRunning(boolean run) {
        running = run;
    }

    @Override
    public void run() {
        while (running) {
            Canvas c = null;
            try {
                c = view.getHolder().lockCanvas();
                synchronized (view.getHolder()) {
                    view.drawCanvas(c);
                }
            } finally {
                if (c != null) {
                    view.getHolder().unlockCanvasAndPost(c);
                }
            }
        }
    }
}

MainActivity.java

public class MainActivity extends Activity {

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);
        LinearLayout ll = (LinearLayout) findViewById(R.id.main);
        ll.setLayoutParams(new LinearLayout.LayoutParams(640, 400));
    }
}

Main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:gravity="center_horizontal|top">

    <LinearLayout
        android:id="@+id/main"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="vertical">

        <com.android.GameView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" />
    </LinearLayout>
</LinearLayout>

结果是http://oi57.tinypic.com/15znrpy.jpg

如果我注释GameView onDraw方法并添加canvas.drawBitmap(背景，0，0，null)；到drawCanvas，结果将是http://oi60.tinypic.com/t0g802.jpg

Answer 1

没有一种具体的方法来设置SurfaceView的背景。

如果您在onDraw中设置了一个背景，然后在onDraw之外的某个地方绘图到画布上，它将调用onDraw并在刚刚绘制的任何内容上绘制背景。

每次重新绘制背景不会占用大量内存，前提是您没有尝试在UI线程上这样做。

另外，我不太清楚你所说的“左上角2-3dp被删除”和“左上角空空间”是什么意思。你能把这张照片和你试过的代码一起贴出来吗？