Android 解决Handler在运行时加载报空指针异常

public class WeakReferenceHandler<T> extends Handler {

private final WeakReference<T> mReference;

public WeakReferenceHandler(T referencedObject) {
mReference = new WeakReference<>(referencedObject);
}

public WeakReferenceHandler(Looper looper, T referencedObject) {
super(looper);
mReference = new WeakReference<>(referencedObject);
}

protected T getReferencedObject() {
return mReference.get();
}

}

private RangHandler mHandler;

/**
* 处理异步操作
*/
private static class RangHandler extends WeakReferenceHandler<RankingFragment> {

public RangHandler(RankingFragment referencedObject) {
super(referencedObject);
// TODO Auto-generated constructor stub
}

//编写自己的需要执行的任务
@Override
public void handleMessage(Message msg) {
RankFragment fragment = getReferencedObject();
if (fragment != null && fragment.getActivity() != null) {
switch (msg.what) {
case MSG_SHOW:
fragment.refreshed();
if (fragment.mRankDataAdapter != null) {
fragment.mRankDataAdapter.notifyDataSetChanged();
}
break;
case MSG_ERROR:
if (fragment.isAdded())
Toast.makeText(fragment.getActivity(), R.string.error_response, Toast.LENGTH_SHORT).show();
fragment.refreshedFail();
break;
default:
if (fragment.isAdded())
Toast.makeText(fragment.getActivity(), R.string.error_response, Toast.LENGTH_SHORT).show();
break;
}
}
}
}

3.在onCreateView方法中实例化Handler

mHandler = new RangHandler(this);

4.需要调用的地方时

mHandler.sendEmptyMessage(MSG_SHOW);