android--如何将View转换成Bitmap

使用setDrawingCacheEnabled(boolean enabled);

/**
     * 
Enables or disables the drawing cache. When the drawing cache is enabled, the next call
     * to {@link #getDrawingCache()} or {@link #buildDrawingCache()} will draw the view in a
     * bitmap. Calling {@link #draw(android.graphics.Canvas)} will not draw from the cache when
     * the cache is enabled. To benefit from the cache, you must request the drawing cache by
     * calling {@link #getDrawingCache()} and draw it on screen if the returned bitmap is not
     * null.
     *
     * 
Enabling the drawing cache is similar to
     * {@link #setLayerType(int, android.graphics.Paint) setting a layer} when hardware
     * acceleration is turned off. When hardware acceleration is turned on, enabling the
     * drawing cache has no effect on rendering because the system uses a different mechanism
     * for acceleration which ignores the flag. If you want to use a Bitmap for the view, even
     * when hardware acceleration is enabled, see {@link #setLayerType(int, android.graphics.Paint)}
     * for information on how to enable software and hardware layers.
     *
     * 
This API can be used to manually generate
     * a bitmap copy of this view, by setting the flag to true and calling
     * {@link #getDrawingCache()}.
     *
     * @param enabled true to enable the drawing cache, false otherwise
     *
     * @see #isDrawingCacheEnabled()
     * @see #getDrawingCache()
     * @see #buildDrawingCache()
     * @see #setLayerType(int, android.graphics.Paint)
     */

• 启用或不启用绘图缓存；当启用时，下次调用getDrawingCache()或者buildDrawingCache()将会在bitmap上画出view。当不允许缓存时，调用draw(Canvas
  canvas)将不能根据缓存来画view。为了能够根据缓存来画view，你应该通过调用getDrawingCache()来请求绘图缓存，然后将它画在屏幕上，前提是返回的bitmap不为null。

• 当硬件加速关掉时，启用绘图缓存和setLayerType(int,
  android.graphics.Paint)（设置一个层）相似。当硬件加速打开时，启用绘图缓存对渲染没有影响，因为系统使用了一个不同的机制来加速渲染，这个机制忽略了标志。如果你想给view使用bitmap，即使是硬件加速启用的情况下，可以查看{@link #setLayerType(int, android.graphics.Paint)}来获取更多关于如何启用软件、硬件层的信息。

• 这个API可以被用于手动生成view的位图副本，通过设置标记为true，并且调用getDrawingCache()获取bitmap。

举个栗子：

View view = LayoutInflater.from(mContext).inflate(R.layout.test, null);
view.setDrawingCacheEnabled(true);
view.measure(View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED), View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
view.buildDrawingCache();
Bitmap cacheBitmap = view.getDrawingCache();
Bitmap bitmap = Bitmap.createBitmap(cacheBitmap);