应用程序在关闭时因收到 gcm 消息而崩溃

Question

当我的应用程序关闭时（即用户从“应用程序切换”菜单中关闭），它会在 onMessageReceived() 中崩溃。

这里是onMessageReceived()：

@Override
public void onMessageReceived(String from, Bundle data) {
    String message = data.getString("message");
    from = data.getString("sender");

    File notificationsFile = Constants.getNotificationsFlagFile();
    ...
}

它在最后一行崩溃，给出 null pointer exception:

08-13 21:15:25.535 23201-23216/com.example.myapp E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1 java.lang.ExceptionInInitializerError at com.example.myapp.chatGCM.MyGcmListenerService.onMessageReceived(MyGcmListenerService.java:52) at com.google.android.gms.gcm.GcmListenerService.zzs(Unknown Source) at com.google.android.gms.gcm.GcmListenerService.zzk(Unknown Source) at com.google.android.gms.gcm.GcmListenerService.zza(Unknown Source) at com.google.android.gms.gcm.GcmListenerService.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) at java.lang.Thread.run(Thread.java:841) Caused by: java.lang.NullPointerException at helpers.Constants.(Constants.java:54) at com.example.myapp.chatGCM.MyGcmListenerService.onMessageReceived(MyGcmListenerService.java:52) at com.google.android.gms.gcm.GcmListenerService.zzs(Unknown Source) at com.google.android.gms.gcm.GcmListenerService.zzk(Unknown Source) at com.google.android.gms.gcm.GcmListenerService.zza(Unknown Source) at com.google.android.gms.gcm.GcmListenerService.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) at java.lang.Thread.run(Thread.java:841)

这里是 getNotificationsFlagFile():

public static File getNotificationsFlagFile()
{
    return new File(MainApplication.getAppContext().getFilesDir(), "notifications_"+getSession());
}

最后：

private static String getSession()
{
    File file = new File(MainApplication.getAppContext().getFilesDir(), "session");
    int length = (int) file.length();
    byte[] bytes = new byte[length];
    FileInputStream in = null;
    try {
        in = new FileInputStream(file);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    try {
        try {
            in.read(bytes);
        } catch (IOException e) {
            e.printStackTrace();
        }
    } finally {
        try {
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return (new String(bytes));
}

我使用的只是静态变量和函数。为什么会这样？

Answer 1

From here 你似乎有一个意想不到的行为......可能来自 getAppContext() 函数......尝试改用 getApplicationContext()。

应用程序在关闭时因收到 gcm 消息而崩溃

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