Drawable的getIntrinsicHeight()和getIntrinsicWidth()

版权声明：本文为博主原创文章，未经博主允许不得转载。

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);
  }

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

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

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

 @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);
    }

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 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;
    }

    /**
     * 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;

 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;
 }

   /**
     * 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