WeakReference在Android中的使用

android

定义

• 弱引用：用于非必需对象。被弱引用关联的对象只能生存到下一次垃圾收集发生之前。当垃圾收集器工作时，无论当前内存是否足够，都会回收掉只被弱引用关联的对象。[WeakReference]

1. 非UI线程处理Bitmap（可以替换为其它对象）

以下摘自官网

class BitmapWorkerTask extends AsyncTask {
    private final WeakReference imageViewReference;
    private int data = 0;
    public BitmapWorkerTask(ImageView imageView) {
        // Use a WeakReference to ensure the ImageView can be garbage collected
        imageViewReference = new WeakReference(imageView);
    }
    // Decode image in background.
    @Override
    protected Bitmap doInBackground(Integer... params) {
        data = params[0];
        return decodeSampledBitmapFromResource(getResources(), data, 100, 100));
    }
    // Once complete, see if ImageView is still around and set bitmap.
    @Override
    protected void onPostExecute(Bitmap bitmap) {
        if (imageViewReference != null && bitmap != null) {
            final ImageView imageView = imageViewReference.get();
            if (imageView != null) {
                imageView.setImageBitmap(bitmap);
            }
        }
    }
}

2. 管理Activity与Handler通信

以下为本人项目中的代码片段，完整代码

    static class WeakReferenceHander extends Handler {
        private final WeakReference<ShareUploadActivity> mActivity;
        public WeakReferenceHander(ShareUploadActivity activity) {
            mActivity = new WeakReference<ShareUploadActivity>(activity);
        }
        @Override
        public void handleMessage(Message msg) {
            if (mActivity.get() != null) {
               mActivity.get().handleReceiveMessage(msg);
            }
        }
    }