Android 解决Handler在运行时加载报空指针异常

1.可自定义一个这样的WeakReferenceHandler

public class WeakReferenceHandler extends Handler {    private final WeakReference 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();    }}

2.在Fragment创建一个新Handler并继承WeakReferenceHandler

private RangHandler mHandler;

/** * 处理异步操作 */private static class RangHandler extends WeakReferenceHandler {    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);

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