[移动开发]Android 关于Bitmap的Mutable特征

在创建Bitmap时使用了如下方式：

bp = BitmapFactory.decodeResource(getResources(), R.drawable.test)；

后面在进行处理时报了异常

     Caused by: java.lang.IllegalStateException
        at android.graphics.Bitmap.setPixels(Bitmap.java:2222)

查看Bitmap源码，发现isMutable方法校验不过。

   /**
     * <p>Replace pixels in the bitmap with the colors in the array. Each element
     * in the array is a packed int representing a non-premultiplied ARGB
     * {@link Color} in the {@link ColorSpace.Named#SRGB sRGB} color space.</p>
     *
     * @param pixels   The colors to write to the bitmap
     * @param offset   The index of the first color to read from pixels[]
     * @param stride   The number of colors in pixels[] to skip between rows.
     *                 Normally this value will be the same as the width of
     *                 the bitmap, but it can be larger (or negative).
     * @param x        The x coordinate of the first pixel to write to in
     *                 the bitmap.
     * @param y        The y coordinate of the first pixel to write to in
     *                 the bitmap.
     * @param width    The number of colors to copy from pixels[] per row
     * @param height   The number of rows to write to the bitmap
     *
     * @throws IllegalStateException if the bitmap is not mutable
     * @throws IllegalArgumentException if x, y, width, height are outside of
     *         the bitmap's bounds.
     * @throws ArrayIndexOutOfBoundsException if the pixels array is too small
     *         to receive the specified number of pixels.
     */
    public void setPixels(@ColorInt int[] pixels, int offset, int stride,
            int x, int y, int width, int height) {
        checkRecycled("Can't call setPixels() on a recycled bitmap");
        if (!isMutable()) {
            throw new IllegalStateException();
        }
        if (width == 0 || height == 0) {
            return; // nothing to do
        }
        checkPixelsAccess(x, y, width, height, offset, stride, pixels);
        nativeSetPixels(mNativePtr, pixels, offset, stride,
                        x, y, width, height);
    }

而mutable 作用 ：主要是控制bitmap的setPixel方法能否使用，即外界能否修改bitmap的像素。

解决方案，则需要使用copy方法的第二个参数将该Bitmap的mutable改为true。

bp = BitmapFactory.decodeResource(getResources(), R.drawable.test1).copy(Bitmap.Config.ARGB_8888, true);