Question

也许我无法找到答案的原因是，我正在以错误的方式提出这个问题，但我仍然希望有人可以回答这个问题。

我有一个带有ListView的MainActivity，它在处理后从数据库中显示一些值：

public class MainActivity extends Activity {
ListView mainViewList;
    CTTObjectsArrayAdapter arrayAdapter;
    ArrayList<CTTObject> cttObjects = null;
    public UpdateObjectResultReceiver updateObjectReceiver;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Update all the Objects in the DB
        CTTUtilities.updateAllObjects(context, updateObjectReceiver);
        // DB stuff
        CTTObjectsDataSource dataSource = new CTTObjectsDataSource(context);
        dataSource.open();

        // Initialize ListView
        mainViewList = (ListView) findViewById(R.id.listMain);

        // Initialize our ArrayList
        cttObjects = new ArrayList<CTTObject>();
        cttObjects = dataSource.getAllObjects();
        dataSource.close();

        // Initialize our array adapter notice how it references the
        // listMain.xml layout
        arrayAdapter = new CTTObjectsArrayAdapter(context,
                R.layout.main_list_row_layout, cttObjects);

        // Set the above adapter as the adapter of choice for our list
        mainViewList.setAdapter(arrayAdapter);
}

现在，我需要的是，当updateObjectReceiver变量从我启动的Intent Service收到答案并更新数据库时，调用以下代码片段来更新ListView：

cttObjects.clear();
CTTObjectsDataSource dataSource = new CTTObjectsDataSource(context);
dataSource.open();
cttObjects.addAll(dataSource.getAllObjects());
dataSource.close();
arrayAdapter.notifyDataSetChanged();

我怎么能这样做？

修改

在实现了receiver.send和下面提出的方法之后，应用程序失败了：

07-23 20:30:40.435: W/dalvikvm(3467): threadid=15: thread exiting with uncaught exception (group=0x40c88930)
07-23 20:30:40.435: E/AndroidRuntime(3467): FATAL EXCEPTION: IntentService[UpdateObjectIntentService]
07-23 20:30:40.435: E/AndroidRuntime(3467): java.lang.NullPointerException
07-23 20:30:40.435: E/AndroidRuntime(3467):     at info.hecatosoft.ctttrack2.UpdateObjectIntentService.onHandleIntent(UpdateObjectIntentService.java:89)
07-23 20:30:40.435: E/AndroidRuntime(3467):     at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
07-23 20:30:40.435: E/AndroidRuntime(3467):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-23 20:30:40.435: E/AndroidRuntime(3467):     at android.os.Looper.loop(Looper.java:137)
07-23 20:30:40.435: E/AndroidRuntime(3467):     at android.os.HandlerThread.run(HandlerThread.java:60)

编辑2：

该行失败：receiver.send(STATUS_UPDATED_CHANGED, Bundle.EMPTY);

有问题的代码是：

@Override
    protected void onHandleIntent(Intent arg0) {
        // ---process the received extras to the service call and get the URL
        // from it---
        this.receiver = arg0.getParcelableExtra(RECEIVER_KEY);
        String recTrackNo = arg0.getStringExtra("trackNo");
        Log.i("jbssmDeveloper", "received trackNo=" + recTrackNo);

        String jsonDataString = null;

            jsonDataString = getHTTPJSONData(recTrackNo);

            if (jsonDataString != null) {
                dataSource = new CTTObjectsDataSource(getBaseContext());
                dataSource.open();
                CTTObject cttObject = dataSource
                        .getObjectWithTrackNo(recTrackNo);
                dataSource.close();
                updateDB(cttObject, jsonDataString);
                receiver.send(STATUS_UPDATED_CHANGED, Bundle.EMPTY);
            }
            receiver.send(STATUS_ERROR, Bundle.EMPTY);
        this.stopSelf();
    }

Answer 1

覆盖onReceiveResult(int, Bundle)的{{1}}：

UpdateObjectResultReceiver

初始化ResultReceiver时，您必须传递活动的上下文。

修改

@Override protected void onReceiveResult (int resultCode, Bundle resultData) { cttObjects.clear(); CTTObjectsDataSource dataSource = new CTTObjectsDataSource(context); dataSource.open(); cttObjects.addAll(dataSource.getAllObjects()); dataSource.close(); arrayAdapter.notifyDataSetChanged(); }

Answer 2

而不是创建和UpdateObjectResultReceiver，使其成为一个接口，然后在您的活动中实现它。然后将回调方法添加到您的活动中并在其中运行代码。

如何在IntentService向ResultReceiver返回内容后更新Android中的ListView

2 个答案: