Android保存View到本地图片

最近在看Android的系统源码，在看到View的源码的时候，无意间看到了在源码中有这么一个函数：

 /**
     * Create a snapshot of the view into a bitmap.  We should probably make
     * some form of this public, but should think about the API.
     */
    Bitmap createSnapshot(Bitmap.Config quality, int backgroundColor, boolean skipChildren) {

通过注释，我可以知道，这个函数就是用于将View绘制的内容保存到一个Bitmap中进行返回，用户需要的话可以将该

Bitmap保存到任意位置。看到这里，我突然想起来，以前用过网上的保存View到图片的代码，这里先贴上两份代码：

1.网络上的保存代码：

Bitmap bitmap = Bitmap.createBitmap(ivTest.getMeasuredWidth(), ivTest.getMeasuredHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas();
        canvas.setBitmap(bitmap);
        ivTest.draw(canvas);

2.View中的createSnapshot中的代码：

代码稍微有点长，但是考虑的方面比较多。所以，效果也比较好，后面会有对比：

/**
     * Create a snapshot of the view into a bitmap.  We should probably make
     * some form of this public, but should think about the API.
     */
    Bitmap createSnapshot(Bitmap.Config quality, int backgroundColor, boolean skipChildren) {
        int width = mRight - mLeft;
        int height = mBottom - mTop;

        final AttachInfo attachInfo = mAttachInfo;
        final float scale = attachInfo != null ? attachInfo.mApplicationScale : 1.0f;
        width = (int) ((width * scale) + 0.5f);
        height = (int) ((height * scale) + 0.5f);

        Bitmap bitmap = Bitmap.createBitmap(mResources.getDisplayMetrics(),
                width > 0 ? width : 1, height > 0 ? height : 1, quality);
        if (bitmap == null) {
            throw new OutOfMemoryError();
        }

        Resources resources = getResources();
        if (resources != null) {
            bitmap.setDensity(resources.getDisplayMetrics().densityDpi);
        }

        Canvas canvas;
        if (attachInfo != null) {
            canvas = attachInfo.mCanvas;
            if (canvas == null) {
                canvas = new Canvas();
            }
            canvas.setBitmap(bitmap);
              .........
            attachInfo.mCanvas = null;
        } else {
            // This case should hopefully never or seldom happen
            canvas = new Canvas(bitmap);
        }

        if ((backgroundColor & 0xff000000) != 0) {     //用于处理背景
            bitmap.eraseColor(backgroundColor);
        }

        .........

        // Fast path for layouts with no backgrounds
        if ((mPrivateFlags & PFLAG_SKIP_DRAW) == PFLAG_SKIP_DRAW) {
            dispatchDraw(canvas);
            if (mOverlay != null && !mOverlay.isEmpty()) {
                mOverlay.getOverlayView().draw(canvas);
            }
        } else {
            draw(canvas);
        }

        mPrivateFlags = flags;

        canvas.restoreToCount(restoreCount);
        canvas.setBitmap(null);

        if (attachInfo != null) {
            // Restore the cached Canvas for our siblings
            attachInfo.mCanvas = canvas;
        }

        return bitmap;
    }

通过对比，可以看出，两个代码的实现思路相似，createSnapshot中的代码对背景使用eraseColor进行了处理。

同时，看到这里，我发现，在注释中也没有API的限制，同时，官方也有意将改API暴漏出来，想着练练手的目的，我想着用反射看看能不能调用到这个函数呢？答案肯定是可以的，下面直接上我的代码：

private void saveViewUserInvoke(){
        Class cls = ivTest.getClass();
        while (!cls.getName().equals("android.view.View")){
            cls = cls.getSuperclass();
        }

        try {
            Method method = cls.getDeclaredMethod("createSnapshot", new Class[]{Bitmap.Config.class, int.class, boolean.class});
            method.setAccessible(true);
            Bitmap bitmap = (Bitmap) method.invoke(ivTest, Bitmap.Config.ARGB_8888, Color.WHITE, false);
            saveBitmapToFile(bitmap);  //自定义的保存函数
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

这样就可以简单的，并且完美的保存图片到本地了。下面贴上效果图：右边是保存后的效果。