Question

我正在构建一个室内导航应用程序，使用Dijkstra算法和可用的地图来指导校园内的人。当我在可用地图上绘制零件图时，我创建了一个CustomView，并按照互联网上有关如何在Canvas中绘制线条的说明进行操作。这是“MyImageView.java”的代码

public class MyImageView extends SurfaceView implements SurfaceHolder.Callback {
private CanvasThread canvasThread;

public MyImageView(Context context) {
    super(context);
    getHolder().addCallback(this);
    canvasThread = new CanvasThread(getHolder(), this);
    setFocusable(true);
}

public MyImageView(Context context, AttributeSet attrs){
    super(context,attrs);
    getHolder().addCallback(this);
    canvasThread = new CanvasThread(getHolder(), this);
    setFocusable(true);

}

protected void onDraw(Canvas canvas){
    Log.d("ondraw", "ondraw");
    Paint p = new Paint();
    Bitmap mapImg = BitmapFactory.decodeResource(getResources(), R.drawable.map);
    Bitmap mapImgResized = Bitmap.createScaledBitmap(mapImg,canvas.getWidth(),canvas.getHeight(), true);
    canvas.drawColor(Color.BLACK);
    canvas.drawBitmap(mapImgResized, 0, 0, null);
    p.setColor(Color.RED);
    p.setStrokeWidth(6f);
    p.setStyle(Paint.Style.STROKE);
    canvas.drawLine(524,995,524,495,p);
    canvas.drawLine(524,495,410,495,p);
    canvas.drawLine(410,495,396,418,p);
    canvas.drawLine(396,418,157,418,p);
    canvas.drawLine(157,418,157,267,p);
    canvas.drawLine(157,267,114,267,p);
    canvas.drawLine(114,267,114,244,p);
    canvas.drawLine(114,244,72,244,p);
}

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

}

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

}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    boolean retry = true;
    canvasThread.setRunning(false);
    while(retry){
        try {
            canvasThread.join();
            retry = false;
        }
        catch (InterruptedException e){

        }
    }

}

}

这是“CanvasThread.java”的代码

public class CanvasThread extends Thread {
private SurfaceHolder surfaceHolder;
private MyImageView myImageView;
private boolean run = false;

public CanvasThread(SurfaceHolder s, MyImageView m){
    surfaceHolder = s;
    myImageView = m;
}

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

public void run(){
    Canvas c;
    while(run){
        c = null;
        try
        {
            c = surfaceHolder.lockCanvas(null);
            synchronized (surfaceHolder){
                myImageView.onDraw(c);
            }
        }
        finally {
            if(c!=null){
                surfaceHolder.unlockCanvasAndPost(c);
            }
        }
    }
}

}

ImageView的XML部分

<?xml version="1.0" encoding="utf-8"?>

<com.example.borntowin.draft.MyImageView
    android:id="@+id/main_imagemap"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="80dp"/>

此代码工作正常，但在结果中我可以看到只要模拟器正在运行，onDraw方法就会运行。有人能为我解释原因吗？它与CanvasThread有什么关系吗？我使用的是Android Studio 1.5。

由于CanvasThread，onDraw方法永远运行

0 个答案: