1.首先在AndroidManifest.xml中申请权限

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>

2.截取指定View的内容

   public Bitmap viewShot() {
        //获取window最底层的view,这里我们指定为截取DecorView
        View view = getWindow().getDecorView();
        view.buildDrawingCache();

        //状态栏高度
        Rect rect = new Rect();
        view.getWindowVisibleDisplayFrame(rect);
        int stateBarHeight = rect.top;
        Display display = getWindowManager().getDefaultDisplay();

        //获取屏幕宽高
        int widths = display.getWidth();
        int height = display.getHeight();

        //设置允许当前窗口保存缓存信息
        view.setDrawingCacheEnabled(true);

        //去掉状态栏高度
        Bitmap bitmap = Bitmap.createBitmap(view.getDrawingCache(), 0, stateBarHeight, widths, height - stateBarHeight);

        view.destroyDrawingCache();
        return bitmap;
    }

3.将Bitmap保存到指定目录

    public static void saveImage(Bitmap bmp) {
        File appDir = new File(Environment.getExternalStorageDirectory(), "Boohee");
        if (!appDir.exists()) {
            appDir.mkdir();
        }
        String fileName = System.currentTimeMillis() + ".png";
        File file = new File(appDir, fileName);
        try {
            FileOutputStream fos = new FileOutputStream(file);
            bmp.compress(Bitmap.CompressFormat.PNG, 100, fos);
            fos.flush();
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

扩展

1.Drawable ----> Bitmap

BitmapDrawable bd = (BitmapDrawable) drawable;
Bitmap bm= bd.getBitmap();

2.Bitmap--------> Drawable:
第一种：

Drawable drawable = new BitmapDrawable(bitmap); 

第二种：

BitmapDrawable bd= new BitmapDrawable(getResource(), bm);