android – 如何更新具有从Sqlite填充的Gridview的Fragment

我有一个带有两个标签的ViewPager,它们包含片段.在第一个片段中,我有一个Gridview,其中填充了Sqlite Db.

我的Activity中有一个自定义alertdialog,它是Fragments的父级.

当alertdialog关闭时,它会添加/删除/更新Sqlite Db：

DataBaseHelper dbh = DataBaseHelper(this);
...
positiveButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        dbh.addVal(new TheData(editName.getText().toString(), editAge.getText().toString())); //adds a row to the Sqlite Db
        dialog.dismiss();
        //on dismiss, refresh the Fragment, which in turn will display the updated GridView.
    }
});
...

如何更新完成以下内容：

//on dismiss, refresh the Fragment, which in turn will display the updated GridView.

解决方法:

您可以将Intents and Intent Filters与Broadcast Receiver一起使用
 为了这.

>在要更新数据的片段中创建BroadcastReceiver实例.
>创建一个IntentFilter并为其设置一个操作字符串(可能是’db.update’)并将其注册到您的应用程序上下文中(您可以通过调用getActivity()通过您的片段来完成此操作.getApplicationContext().registerReceiver(receiver,filter) .
>在AlertDialog中,更新数据库后,使用您在上面设置的相同操作字符串(在我们的示例中为“db.update”)创建一个Intent,并使用上下文将其发送出去(getActivity().getApplicationContext().sendBroadcast (意图)).您的BroadcastReceiver的onReceive()方法将在您的片段中调用,您可以调用该方法刷新或重新加载您的数据.请参阅以下示例代码：

说这是你的片段

public class YourFragment extends Fragment {

private GridView mGridView;
private BaseAdapter mAdapter;
private BroadcastReceiver mReceiver;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    //inflate view as usual
    View view = inflater.inflate(R.layout.yourlayour, container, false);
    ...

    //create instance of broadcast receiver
    mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) { //when intent is receiver, this method is called
            if(intent.getAction().contentEquals("db.update")){
                //update intent received, call method to refresh your content loader
                refreshFragment();
            }
        }
    };

    //create a new intent filter
    IntentFilter mDataUpdateFilter = new IntentFilter("db.update");

    //register our broadcast receiver and intent filter
    getActivity().getApplicationContext().registerReceiver(mReceiver, mDataUpdateFilter);
    return view;
}

@Override
public void onDestroy() {
    super.onDestroy();
    //never forget to unregister the receiver when you're done, it could cause your app to crash
    //if it receives an intent and calls null pointing methods in your code
    getActivity().getApplicationContext().unregisterReceiver(mReceiver);
}  }

然后在上面的AlertDialog中,通过以下方式将意图发送给此接收器：

DataBaseHelper dbh = DataBaseHelper(this);
        ...
        positiveButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dbh.addVal(new TheData(editName.getText().toString(), editAge.getText().toString())); //adds a row to the Sqlite Db


                //Create an intent with our action
                Intent updateIntent = new Intent("db.update");

                //send the intent by
                getContext().getApplicationContext().sendBroadcast(updateIntent);
                dialog.dismiss();
            }
        });
        ...

片段被销毁时,不要忘记取消注册广播接收器.调用getActivity().getApplicationContext().unregisterReceiver(receiver);在你的onDestroy()方法中.

我还应该指出,即使你从后台线程发送你的意图,你的广播接收器的onReceive()方法也会在主线程上被调用.

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