解决方法：将handler声明为static静态方法

在activity中：

private final MyHandler handler=new MyHandler(this);//在activity中声明handler

private static class MyHandler extends Handler {

private final WeakReference mActivityReference;

MyHandler(Activity activity) {

this.mActivityReference=new WeakReference<>(activity);

}

@Override

public void handleMessage(Message msg) {

super.handleMessage(msg);

final MainActivity activity = (MainActivity)mActivityReference.get();//获取弱引用队列中的activity

if(activity!=null){

switch(msg.what) {//获取消息，更新UI

}

}

}

}

//消息队列里面的消息移除

@Override

protected voidonDestroy() {

super.onDestroy();

_handler.removeCallbacksAndMessages(null);

context=null;

}

---

在fragment中

private final MyHandler handler=new MyHandler(this);//在activity中声明handler

private static class MyHandler extends Handler {

private final WeakReference mFragmentReference;

MyHandler(Fragment fragment) {

this.mFragmentReference=new WeakReference<>(fragment);

}

@Override

public void handleMessage(Message msg) {

super.handleMessage(msg);

final MainFragment fragment= (MainFragment)mFragmentReference.get();

if(fragment!=null){

switch(msg.what) {//获取消息，更新UI

}

}

}

}

//消息队列里面的消息移除

@Override

protected voidonDestroy() {

super.onDestroy();

_handler.removeCallbacksAndMessages(null);

}