【android】把view保存为图片的方法以及解决保存后图片背景变黑色的问题

上代码：

public class MainActivity extends Activity {
	ImageView imgView;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		imgView = (ImageView) findViewById(R.id.imageView);
		imgView.setDrawingCacheEnabled(true);
		// this is the important code :)
		// Without it the view will have a dimension of 0,0 and the bitmap will be null
		imgView.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
		            MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
		imgView.layout(0, 0, imgView.getMeasuredWidth(), imgView.getMeasuredHeight());
		Bitmap bitmap = Bitmap.createBitmap(imgView.getDrawingCache());
		imgView.setDrawingCacheEnabled(false);
		String strPath ="/testSaveView/"+UUID.randomUUID().toString()+".png";
		if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))
		 {
			 File sdCardDir=Environment.getExternalStorageDirectory();
			 FileOutputStream fos = null;
			 try{
				 File file = new File(sdCardDir,strPath);
				 if (!file.getParentFile().exists()) {
					 file.getParentFile().mkdirs();
				 }
				 fos = new FileOutputStream(file);

				//当指定压缩格式为PNG时保存下来的图片显示正常
				 bitmap.compress(CompressFormat.JPEG, 100, fos); 

				//当指定压缩格式为JPEG时保存下来的图片背景为黑色
//				 bitmap.compress(CompressFormat.JPEG, 100, fos);
				 fos.flush();
			 }catch(Exception e){
				 e.printStackTrace();
			 }finally{
				 try {
					 fos.close();
				 } catch (IOException e) {
					 e.printStackTrace();
				 }
			 }
		 }
	}
}

activity_main.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:scaleType="centerInside"
        android:src="@drawable/ic_launcher"/>
</LinearLayout>

需要注意两个问题：

一、调用getDrawingCache()前先要测量，否则的话得到的bitmap为null，这个我在OnCreate()、OnStart()、OnResume()方法里都试验过。

二、当调用bitmap.compress(CompressFormat.JPEG, 100, fos);保存为图片时发现图片背景为黑色，如下图：

这时只需要改成用png保存就可以了，bitmap.compress(CompressFormat.PNG, 100, fos);,如下图：