设置图像背景SurfaceView，得到黑屏 [英] Setting image background in SurfaceView, getting black screen

问题描述

好了，所以我试着去一个SurfaceView的背景设定为一个JPG文件。但它似乎并不想画的形象，我得到的是一个黑色的屏幕。

Okay so Im trying to set the background of a SurfaceView to a JPG file. But it doesn't seem to want to draw the image, and all I get is a black screen.

下面：我的code：

    public class FloorplanActivity extends Activity{

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    MapView mapView = new MapView(getApplicationContext());
    setContentView(mapView);


}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.floorplan, menu);
    return true;
}

class MapView extends SurfaceView{

    Rect testRectangle1 = new Rect(0, 0, 50, 50);
    Bitmap scaled;
    int x;
    int y;

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

    }

    public void surfaceCreated(SurfaceHolder arg0){
        Bitmap background = BitmapFactory.decodeResource(getResources(), R.drawable.floorplan);
        float scale = (float)background.getHeight()/(float)getHeight();
        int newWidth = Math.round(background.getWidth()/scale);
        int newHeight = Math.round(background.getHeight()/scale);
        scaled = Bitmap.createScaledBitmap(background, newWidth, newHeight, true);
    }

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

不知道为什么它不会画我都保存在绘制-MDPI文件夹中的布局规划的形象。

Not sure why it won't draw the "floorplan" image I have saved in the drawable-mdpi folder.

任何人有什么建议吗？

感谢。

编辑：做一些调试和断点后，它似乎像缩放变量变成无限出于某种原因，因此在newWidth和newHeight变量变得小于0，应用程序崩溃

After doing some debugging with breakpoints, it seems like the "scaled" variable becomes "Infinity" for some reason and as such the newWidth and newHeight variables become less than 0 and the application crashes.

这是只有当我移动整个surfaceCreated到contstructor，如果我离开了code因为是在这里那么它不beyind显示黑屏做任何事情。

This is only if I move the entire surfaceCreated into the contstructor, if I leave the code as is here then it doesn't do anything beyind displaying a black screen.

不知道是什么原因引起的，虽然这样做......

No idea what's causing it to do that though...

推荐答案

首先，你应该实现SurfaceHolder.Callback接口与你的MapView类，并将其设置为一个回调的SurfaceHolder，使应用程序调用你的onSurfaceCreated（）梅托德。 其次，如果你希望你的OnDraw（）方法被调用，然后调用setWillNotDraw（假）在图形页面的构造。

First, you should implement SurfaceHolder.Callback interface with your MapView class and set it as a callback for its SurfaceHolder to make the app call your onSurfaceCreated() metod. Second, if you want your onDraw() method to be called, then call setWillNotDraw(false) in your MapView's constructor.

我已经做了如下：

public class MapView extends SurfaceView implements SurfaceHolder.Callback {

    private Bitmap scaled;

    public MapView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setWillNotDraw(false);
        getHolder().addCallback(this);
    }

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

    @Override
    public void surfaceCreated(SurfaceHolder arg0) {
        Bitmap background = BitmapFactory.decodeResource(getResources(), R.drawable.dr);
        float scale = (float) background.getHeight() / (float) getHeight();
        int newWidth = Math.round(background.getWidth() / scale);
        int newHeight = Math.round(background.getHeight() / scale);
        scaled = Bitmap.createScaledBitmap(background, newWidth, newHeight, true);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // TODO Callback method contents
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Callback method contents
    }
}

和它工作得很好。 注意：移至图形页面类到一个单独的* .java文件。 更新表复印件移动

And it works well. NOTE: Moved MapView class to a separate *.java file. Update Watch Duplicate Copy Move

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