将视图添加到窗口时如何获取视图宽度和高度？

Posted 2023-02-26

【中文标题】将视图添加到窗口时如何获取视图宽度和高度？

【英文标题】：How to get view width and height when I added it to window?

【发布时间】：2015-07-23 06:27:53

【问题描述】：

我要写一个服务在后台做截图，所以我应该使用服务来做。在这些代码中，我无法创建位图，因为我无法获取宽度和高度

@Override
public void onCreate() 
    super.onCreate();

    try 
        mView = new LinearLayout(this);
        mView.setBackgroundColor(0);
        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                WindowManager.LayoutParams.MATCH_PARENT,
                WindowManager.LayoutParams.MATCH_PARENT,
                WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,
                0 | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                        | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
                        | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
                        | WindowManager.LayoutParams.FLAG_LAYOUT_INSET_DECOR
                        | WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED,
                PixelFormat.TRANSLUCENT);
        WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
        wm.addView(mView, params);


        //all return 0
        int w = mView.getWidth();
        int h = mView.getHeight();
        w = mView.getMeasuredWidth();
        h = mView.getMeasuredHeight();


        mView.measure(View.MeasureSpec.makeMeasureSpec(
                        View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED),
                View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
        mView.layout(0, 0, mView.getMeasuredWidth(),
                mView.getMeasuredHeight());
        mView.setDrawingCacheEnabled(true);
        mView.buildDrawingCache();
        Bitmap bitmap = Bitmap.createBitmap(mView.getMeasuredWidth(),
                mView.getMeasuredHeight(), Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(bitmap);
        Paint paint = new Paint();
        int height = bitmap.getHeight();
        canvas.drawBitmap(bitmap, 0, height, paint);
        mView.draw(canvas);

        if (bitmap != null) 
            try 
                String filePath = Environment.getExternalStorageDirectory()
                        .toString();
                OutputStream out = null;
                File file = new File(filePath, "/mViewScreenShot.png");
                Log.v("0",file.getPath());
                out = new FileOutputStream(file);

                bitmap.compress(Bitmap.CompressFormat.PNG, 50, out);
                out.flush();
                out.close();
                bitmap.recycle();
             catch (Exception e) 
                e.printStackTrace();
            
        

    
    catch(Exception e)
    
        stopSelf();
    
    stopSelf();

我尝试了getWidth和getMeasuredWidth，它们也返回0

int w = mView.getWidth();
int h = mView.getHeight();
w = mView.getMeasuredWidth();
h = mView.getMeasuredHeight();

而且我在getMeasuredWidth和getMeasuredHeight之前也试过这个，还是不行。

mView.measure(MeasureSpec.UNSPECIFIED,MeasureSpec.UNSPECIFIED)

【问题讨论】：

查看link

【参考方案1】：

绘图后视图会知道它的暗淡。试试这个：

mView.post(new Runnable
    @Override
    public void run() 
        width = mView.getWidth();
        height = mView.getHeight();
    
);

【参考方案2】：

您可以使用 ViewTreeObserver 获取视图的宽度和高度。您可以使用它的 onCreate 方法，如下所示：

LinearLayout layout = (LinearLayout)findViewById(R.id.YOUR_VIEW_ID);
ViewTreeObserver vto = layout.getViewTreeObserver(); 
vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener()  
    @Override 
    public void onGlobalLayout()  
        this.layout.getViewTreeObserver().removeGlobalOnLayoutListener(this); 
        int width  = layout.getMeasuredWidth();
        int height = layout.getMeasuredHeight(); 

     
);

【讨论】：

这个答案也应该是接受的答案，但是.post更简单，所以我接受这个答案。

【参考方案3】：

getMeasuredWidth() 和 getMeasuredHeight() 不会返回非零值，除非您调用 measure() first。

之后，您可以使用测量值调用layout() 并从getWidth() 和getHeight() 中获取正确的值。

mView.measure(View.MeasureSpec.makeMeasureSpec(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED), View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
mView.layout(0, 0, mView.getMeasuredWidth(), mView.getMeasuredHeight());
int w = mView.getWidth();
int h = mView.getHeight();
w = mView.getMeasuredWidth();
h = mView.getMeasuredHeight();

【讨论】：

onLayout 是受保护的访问。

@CLSo 这是我的错字，抱歉。您应该调用具有公共访问权限的 layout()。这会在调用两个同步方法 measure() 和 layout() 后立即为您提供所有视图的尺寸。