RecyclingImageView.java

package com.android.pc.ioc.image;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.LayerDrawable;
import android.util.AttributeSet;
import android.widget.ImageView;


/**
 * 自定义imageview.
 */
public class RecyclingImageView extends ImageView {

    public RecyclingImageView(Context context) {
        super(context);
    }

    public RecyclingImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public RecyclingImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs,defStyle);
    }
    
    /**
     * @see android.widget.ImageView#onDetachedFromWindow()
     */
    @Override
    protected void onDetachedFromWindow() {
        // 组件从屏幕移除
        setImageDrawable(null);
        super.onDetachedFromWindow();
    }
    
    /**
     * @see android.widget.ImageView#setImageDrawable(android.graphics.drawable.Drawable)
     */
    @Override
    public void setImageDrawable(Drawable drawable) {
        // 获取之前的图片
        final Drawable previousDrawable = getDrawable();

        // 设置新的图片
        super.setImageDrawable(drawable);

        // 通知新的图片刷新
        notifyDrawable(drawable, true);

        // 把之前的图片取消
        notifyDrawable(previousDrawable, false);
    }

    /**
     * 对于bitmap 的计数进行修改
     *
     * @param drawable
     * @param isDisplayed
     */
    private static void notifyDrawable(Drawable drawable, final boolean isDisplayed) {
        if (drawable instanceof RecyclingBitmapDrawable) {
            ((RecyclingBitmapDrawable) drawable).setIsDisplayed(isDisplayed);
        } else if (drawable instanceof LayerDrawable) {
            LayerDrawable layerDrawable = (LayerDrawable) drawable;
            for (int i = 0, z = layerDrawable.getNumberOfLayers(); i < z; i++) {
                notifyDrawable(layerDrawable.getDrawable(i), isDisplayed);
            }
        }
    }
}