Drawable的getIntrinsicHeight()和getIntrinsicWidth()

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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：

1. private void computeBitmapSize() {
2. mBitmapWidth = mBitmap.getScaledWidth(mTargetDensity);
3. mBitmapHeight = mBitmap.getScaledHeight(mTargetDensity);
4. }

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

1. @Override
2. public int getIntrinsicWidth() {
3. return mBitmapWidth;
4. }
5. @Override
6. public int getIntrinsicHeight() {
7. return mBitmapHeight;
8. }

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

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

1. private BitmapDrawable(BitmapState state, Resources res) {
2. mBitmapState = state;
3. if (res != null) {
4. mTargetDensity = res.getDisplayMetrics().densityDpi;
5. } else if (state != null) {
6. mTargetDensity = state.mTargetDensity;
7. } else {
8. mTargetDensity = DisplayMetrics.DENSITY_DEFAULT;
9. }
10. setBitmap(state.mBitmap);
11. }

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;

1. /**
2. * Create an empty drawable, setting initial target density based on
3. * the display metrics of the resources.
4. */
5. public BitmapDrawable(Resources res) {
6. mBitmapState = new BitmapState((Bitmap) null);
7. mBitmapState.mTargetDensity = mTargetDensity;
8. }
9. /**
10. * Create drawable from a bitmap, not dealing with density.
11. * @deprecated Use {@link #BitmapDrawable(Resources, Bitmap)} to ensure
12. * that the drawable has correctly set its target density.
13. */
14. @Deprecated
15. public BitmapDrawable(Bitmap bitmap) {
16. this(new BitmapState(bitmap), null);
17. }

 /**
     * 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);
    }

1. /**
2. * Create drawable from a bitmap, setting initial target density based on
3. * the display metrics of the resources.
4. */
5. public BitmapDrawable(Resources res, Bitmap bitmap) {
6. this(new BitmapState(bitmap), res);
7. mBitmapState.mTargetDensity = mTargetDensity;
8. }

    /**
     * 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:

1. public static final int DENSITY_DEFAULT = DENSITY_MEDIUM;

 public static final int DENSITY_DEFAULT = DENSITY_MEDIUM;

在Bitmap中：

1. /**
2. * Convenience method that returns the width of this bitmap divided
3. * by the density scale factor.
4. *
5. * @param targetDensity The density of the target canvas of the bitmap.
6. * @return The scaled width of this bitmap, according to the density scale factor.
7. */
8. public int getScaledWidth(int targetDensity) {
9. return scaleFromDensity(getWidth(), mDensity, targetDensity);
10. }
11. /**
12. * Convenience method that returns the height of this bitmap divided
13. * by the density scale factor.
14. *
15. * @param targetDensity The density of the target canvas of the bitmap.
16. * @return The scaled height of this bitmap, according to the density scale factor.
17. */
18. public int getScaledHeight(int targetDensity) {
19. return scaleFromDensity(getHeight(), mDensity, targetDensity);
20. }
21. /**
22. * @hide
23. */
24. static public int scaleFromDensity(int size, int sdensity, int tdensity) {
25. if (sdensity == DENSITY_NONE || sdensity == tdensity) {
26. return size;
27. }
28. // Scale by tdensity / sdensity, rounding up.
29. return ( (size * tdensity) + (sdensity >> 1) ) / sdensity;
30. }

   /**
     * 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