在View类中的onDraw方法的参数Canvas是View绘制的背景,要将View转换为Bitmap实际上就是让Canvas上的绘制操作绘制到Bitmap上。
View转化为Bitmap也称为截屏,让用户看到的View视图转化为图片的过程。
关于View转化Bitmap涉及到的View类中的方法有:
protected void onDraw(Canvas canvas) public void buildDrawingCache() public void destroyDrawingCache() public Bitmap getDrawingCache() public void setDrawingCacheEnabled(boolean enabled)
下面是常见的几个View截屏的示例:
1.View转Bitmap
public final Bitmap screenShot(View view) { if (null == view) { throw new IllegalArgumentException("parameter can't be null."); } view.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight()); view.setDrawingCacheEnabled(true); view.buildDrawingCache(); Bitmap bitmap = view.getDrawingCache(); return bitmap; }
2. Activity转Bitmap,不带状态栏
public final Bitmap screenShot(Activity activity) { if (null == activity) { throw new IllegalArgumentException("parameter can't be null."); } View view = activity.getWindow().getDecorView(); view.setDrawingCacheEnabled(true); view.buildDrawingCache(); Bitmap b1 = view.getDrawingCache(); Rect frame = new Rect(); view.getWindowVisibleDisplayFrame(frame); int statusBarHeight = frame.top; Point point = new Point(); activity.getWindowManager().getDefaultDisplay().getSize(point); int width = point.x; int height = point.y; Bitmap b2 = Bitmap.createBitmap(b1, 0, statusBarHeight, width, height - statusBarHeight); view.destroyDrawingCache(); return b2; }
3. ScrollView转长Bitmap(类似锤子便签的截长图)
public final Bitmap screenShot(ScrollView scrollView) { if (null == scrollView) { throw new IllegalArgumentException("parameter can't be null."); } int height = 0; Bitmap bitmap; for (int i = 0, s = scrollView.getChildCount(); i < s; i++) { height += scrollView.getChildAt(i).getHeight(); scrollView.getChildAt(i).setBackgroundResource(android.R.drawable.screen_background_light); } bitmap = Bitmap.createBitmap(scrollView.getWidth(), height, Bitmap.Config.ARGB_8888); final Canvas canvas = new Canvas(bitmap); scrollView.draw(canvas); return bitmap; }
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