我正在使用Parse.com服务发送推送通知并让广播接收器接收消息。我想在广播接收器中调用我的活动中的方法来显示Toast消息（实际上我想更新listview内容但是现在我只是使用Toast来检查方法是否被成功调用）而不调用活动。
首先，我按照instruction：
进行操作但它会产生错误：
12-20 20:53:33.892: E/AndroidRuntime(14245): FATAL EXCEPTION: main
12-20 20:53:33.892: E/AndroidRuntime(14245): java.lang.RuntimeException: Unable to start receiver event.planner.services.CustomReceiver: java.lang.NullPointerException
12-20 20:53:33.892: E/AndroidRuntime(14245): at android.app.ActivityThread.handleReceiver(ActivityThread.java:2236)
12-20 20:53:33.892: E/AndroidRuntime(14245): at android.app.ActivityThread.access$1500(ActivityThread.java:130)
12-20 20:53:33.892: E/AndroidRuntime(14245): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1271)
12-20 20:53:33.892: E/AndroidRuntime(14245): at android.os.Handler.dispatchMessage(Handler.java:99)
12-20 20:53:33.892: E/AndroidRuntime(14245): at android.os.Looper.loop(Looper.java:137)
12-20 20:53:33.892: E/AndroidRuntime(14245): at android.app.ActivityThread.main(ActivityThread.java:4745)
12-20 20:53:33.892: E/AndroidRuntime(14245): at java.lang.reflect.Method.invokeNative(Native Method)
12-20 20:53:33.892: E/AndroidRuntime(14245): at java.lang.reflect.Method.invoke(Method.java:511)
12-20 20:53:33.892: E/AndroidRuntime(14245): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
12-20 20:53:33.892: E/AndroidRuntime(14245): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-20 20:53:33.892: E/AndroidRuntime(14245): at dalvik.system.NativeStart.main(Native Method)
12-20 20:53:33.892: E/AndroidRuntime(14245): Caused by: java.lang.NullPointerException
12-20 20:53:33.892: E/AndroidRuntime(14245): at event.planner.services.CustomReceiver.onReceive(CustomReceiver.java:60)
12-20 20:53:33.892: E/AndroidRuntime(14245): at android.app.ActivityThread.handleReceiver(ActivityThread.java:2229)
12-20 20:53:33.892: E/AndroidRuntime(14245): ... 10 more
12-20 20:53:35.883: I/Process(14245): Sending signal. PID: 14245 SIG: 9
12-20 20:53:41.322: E/Trace(15934): error opening trace file: No such file or directory (2)
12-20 20:53:41.615: E/com.parse.PushService(15934): The Parse push service cannot start because Parse.initialize has not yet been called. If you call Parse.initialize from an Activity's onCreate, that call should instead be in the Application.onCreate. Be sure your Application class is registered in your AndroidManifest.xml with the android:name property of your <application> tag.
然后我尝试使用如here所述的静态方法，它会产生以下错误：
12-20 20:18:49.553: E/AndroidRuntime(11779): FATAL EXCEPTION: main
12-20 20:18:49.553: E/AndroidRuntime(11779): java.lang.RuntimeException: Error receiving broadcast Intent { act=com.example.UPDATE_STATUS flg=0x10 (has extras) } in event.planner.services.CustomReceiver@41036bd0
12-20 20:18:49.553: E/AndroidRuntime(11779): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:765)
12-20 20:18:49.553: E/AndroidRuntime(11779): at android.os.Handler.handleCallback(Handler.java:615)
12-20 20:18:49.553: E/AndroidRuntime(11779): at android.os.Handler.dispatchMessage(Handler.java:92)
12-20 20:18:49.553: E/AndroidRuntime(11779): at android.os.Looper.loop(Looper.java:137)
12-20 20:18:49.553: E/AndroidRuntime(11779): at android.app.ActivityThread.main(ActivityThread.java:4745)
12-20 20:18:49.553: E/AndroidRuntime(11779): at java.lang.reflect.Method.invokeNative(Native Method)
12-20 20:18:49.553: E/AndroidRuntime(11779): at java.lang.reflect.Method.invoke(Method.java:511)
12-20 20:18:49.553: E/AndroidRuntime(11779): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
12-20 20:18:49.553: E/AndroidRuntime(11779): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-20 20:18:49.553: E/AndroidRuntime(11779): at dalvik.system.NativeStart.main(Native Method)
12-20 20:18:49.553: E/AndroidRuntime(11779): Caused by: java.lang.NullPointerException
12-20 20:18:49.553: E/AndroidRuntime(11779): at android.widget.Toast.<init>(Toast.java:92)
12-20 20:18:49.553: E/AndroidRuntime(11779): at android.widget.Toast.makeText(Toast.java:238)
12-20 20:18:49.553: E/AndroidRuntime(11779): at event.planner.front.FrontLayout.UpdateList(FrontLayout.java:193)
12-20 20:18:49.553: E/AndroidRuntime(11779): at event.planner.services.CustomReceiver.onReceive(CustomReceiver.java:60)
12-20 20:18:49.553: E/AndroidRuntime(11779): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:755)
12-20 20:18:49.553: E/AndroidRuntime(11779): ... 9 more
12-20 20:18:52.613: I/Process(11779): Sending signal. PID: 11779 SIG: 9
12-20 20:18:58.762: E/Trace(12109): error opening trace file: No such file or directory (2)
12-20 20:18:59.603: E/com.parse.PushService(12109): The Parse push service cannot start because Parse.initialize has not yet been called. If you call Parse.initialize from an Activity's onCreate, that call should instead be in the Application.onCreate. Be sure your Application class is registered in your AndroidManifest.xml with the android:name property of your <application> tag.
如何正确地做到这一点？谢谢。
组合两种方法后的代码：
CustomReceiver.java
public class CustomReceiver extends BroadcastReceiver {
private static final String TAG = "MyCustomReceiver";
public static final String ACTION = "com.example.UPDATE_STATUS";
FrontLayout main = null;
public void setMainActivityHandler(FrontLayout main){
this.main=main;
}
@Override
public void onReceive(Context context, Intent intent) {
String title="";
String alert="";
try {
JSONObject json = new JSONObject(intent.getExtras().getString("com.parse.Data"));
Iterator<?> itr = json.keys();
while (itr.hasNext()) {
String key = (String) itr.next();
if(key.equals("title"))
title = json.getString(key);
if(key.equals("alert"))
alert = json.getString(key);
else
continue;
}
} catch (JSONException e) {
Log.w(TAG, "JSONException: " + e.getMessage());
}
SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss",Locale.US);
Date date = new Date();
NotificationModel nm = new NotificationModel();
nm.setTitle(title);
nm.setAlert(alert);
nm.setDateTime(dateFormat.format(date));
NotificationDS nds = new NotificationDS(context);
nds.insertNotification(nm);
main.UpdateList();
}
}
的AndroidManifest.xml
<application>
.....
<service android:name="com.parse.PushService" />
<receiver android:name="com.parse.ParseBroadcastReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
<action android:name="android.intent.action.USER_PRESENT" />
</intent-filter>
</receiver>
<receiver android:name="event.planner.services.CustomReceiver"
android:exported="false">
<intent-filter>
<action android:name="com.example.UPDATE_STATUS" />
</intent-filter>
</receiver>
</application>
<application android:name="event.planner.services.MyApplication">
</application>
FrontLayout.java
public class FrontLayout extends Activity
{
....
CustomReceiver receiver = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
......
receiver = new CustomReceiver();
receiver.setMainActivityHandler(this);
IntentFilter callInterceptorIntentFilter = new IntentFilter("com.example.UPDATE_STATUS");
registerReceiver(receiver, callInterceptorIntentFilter);
}
public static void UpdateList()
{
Toast.makeText(MyApplication.getAppContext(), "Success!", Toast.LENGTH_SHORT).show();
}
}
MyApplication.java
package event.planner.services;
import android.app.Application;
import android.content.Context;
public class MyApplication extends Application{
private static Context context;
public void onCreate(){
super.onCreate();
MyApplication.context = getApplicationContext();
}
public static Context getAppContext() {
return MyApplication.context;
}
}
答案 0 :(得分：13)
请按照以下步骤操作
Step 1:Declare a Interface class in that BroadcastReceiver
Step 2: Implement that interface in your Activity class...
示例代码：
在CustomReceiver.class里面---------
public interface Listener {
public void onUIChanges();
}
public void setListener(Listener listener) {
CustomReceiver .listener = listener;
}
@Override
public void onReceive(Context context, Intent intent)
{
-------
------
if(listener!=null)
{
listener.onUIChanges();
}
}
FrontLayout.class内部
CustomReceiver.setListener(this); // otherwise null pointer occurs
最后实现那个监听器......