今天遇到一个问题,一个Bitmap封装到BitmapDrawable中 ,BitmapDrawable drawable = new BitmapDrawable(bmp)，

Bitmap.getWidth() != BitmapDrawable.getIntrinsicWidth().导致一些问题：

查看源代码，问题如下：

在BitmapDrawable中,给mBitmapWidth赋值时，要根据density缩放，其默认值是160，mdpi的情况：

 mTargetDensity = DisplayMetrics.DENSITY_DEFAULT;

而在Bitmap的density是240情况下，将缩放：

公式约等于为：drawableDensity * bmpWidth / bmpDensity  ======>>  160 * 72 / 240  ,所以getIntrinsicHeight()为48

在BitmapDrawable中：

 

 

private void computeBitmapSize() {        mBitmapWidth = mBitmap.getScaledWidth(mTargetDensity);        mBitmapHeight = mBitmap.getScaledHeight(mTargetDensity);    }

 

@Override    public int getIntrinsicWidth() {        return mBitmapWidth;    }    @Override    public int getIntrinsicHeight() {        return mBitmapHeight;    }

private BitmapDrawable(BitmapState state, Resources res) {        mBitmapState = state;        if (res != null) {            mTargetDensity = res.getDisplayMetrics().densityDpi;        } else if (state != null) {            mTargetDensity = state.mTargetDensity;        } else {            mTargetDensity = DisplayMetrics.DENSITY_DEFAULT;        }        setBitmap(state.mBitmap);    }

 

在ButtonState中，mTargetDensity的值默认为：

int mTargetDensity = DisplayMetrics.DENSITY_DEFAULT;

注意：res == null时，且state != null时，mTargetDensity = state.mTargetDensity;

 

/**     * Create an empty drawable, setting initial target density based on     * the display metrics of the resources.     */    public BitmapDrawable(Resources res) {        mBitmapState = new BitmapState((Bitmap) null);        mBitmapState.mTargetDensity = mTargetDensity;    }    /**     * Create drawable from a bitmap, not dealing with density.     * @deprecated Use {@link #BitmapDrawable(Resources, Bitmap)} to ensure     * that the drawable has correctly set its target density.     */    @Deprecated    public BitmapDrawable(Bitmap bitmap) {        this(new BitmapState(bitmap), null);    }

    /**     * Create drawable from a bitmap, setting initial target density based on     * the display metrics of the resources.     */    public BitmapDrawable(Resources res, Bitmap bitmap) {        this(new BitmapState(bitmap), res);        mBitmapState.mTargetDensity = mTargetDensity;    }

其中，BitmapDrawable(Bitmap bmp)已经被弃用,如果使用 BitmapDrawable(Bitmap bmp,Resources res)构造函数

 

 

在DisplayMetrics:

 public static final int DENSITY_DEFAULT = DENSITY_MEDIUM;

 

在Bitmap中：

 

/**     * Convenience method that returns the width of this bitmap divided     * by the density scale factor.     *     * @param targetDensity The density of the target canvas of the bitmap.     * @return The scaled width of this bitmap, according to the density scale factor.     */    public int getScaledWidth(int targetDensity) {        return scaleFromDensity(getWidth(), mDensity, targetDensity);    }    /**     * Convenience method that returns the height of this bitmap divided     * by the density scale factor.     *     * @param targetDensity The density of the target canvas of the bitmap.     * @return The scaled height of this bitmap, according to the density scale factor.     */    public int getScaledHeight(int targetDensity) {        return scaleFromDensity(getHeight(), mDensity, targetDensity);    }        /**     * @hide     */    static public int scaleFromDensity(int size, int sdensity, int tdensity) {        if (sdensity == DENSITY_NONE || sdensity == tdensity) {            return size;        }                // Scale by tdensity / sdensity, rounding up.        return ( (size * tdensity) + (sdensity >> 1) ) / sdensity;    }

如此,只有做如下改动：

方法一：

BitmapDrawable bmpDrawable = new BitmapDrawable(bmp,getResources);

方法二：

BitmapDrawable bmpDrawable = new BitmapDrawable(bmp);

bmpDrawable.setTargetDensity(getResources().getResources().getDisplayMetrics());

 

借鉴： http://blog.csdn.net/jason_wks/article/details/8283224

    本文转自 一点点征服   博客园博客，原文链接：http://www.cnblogs.com/ldq2016/p/5377670.html，如需转载请自行联系原作者