将额外内容从 Activity 传递到 Intent 会引发 NullPointerException

Question

这是一个衍生出另一个问题的问题。

我将两个字符串从我的主要活动传递给一个子服务，这很好，但是当主要活动终止时，该服务会抛出 NullPointerException 试图获取这两个字符串。

来自 MainActivity：

Intent i = new Intent(this, PebbleService.class);
i.putExtra("quote", quote[0]);
i.putExtra("author", quote[1]);
startService(i);

来自 PebbleService：

public int onStartCommand(Intent intent, int flags, int startId) {
    super.onStartCommand(intent, flags, startId);

    final String author = intent.getStringExtra("author");
    final String quote = intent.getStringExtra("quote");

    // Define AppMessage behavior
    if (appMessageReciever == null) {
        appMessageReciever = new PebbleKit.PebbleDataReceiver(WATCHAPP_UUID) {

            @Override
            public void receiveData(Context context, int transactionId, PebbleDictionary data) {
                // Always ACK
                PebbleKit.sendAckToPebble(context, transactionId);

                // Send KEY_QUOTE to Pebble
                PebbleDictionary out = new PebbleDictionary();
                out.addString(KEY_QUOTE, quote);
                out.addString(KEY_AUTHOR, author);
                PebbleKit.sendDataToPebble(getApplicationContext(), WATCHAPP_UUID, out);
            }
        };

        // Add AppMessage capabilities
        PebbleKit.registerReceivedDataHandler(this, appMessageReciever);
    }

    return START_STICKY;
}

来自 Logcat 的错误：

05-26 10:29:52.972    4147-4147/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: net.thevgc.quotes, PID: 4147
    java.lang.RuntimeException: Unable to start service net.thevgc.quotes.PebbleService@423eb138 with null: java.lang.NullPointerException
            at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2732)
            at android.app.ActivityThread.access$2100(ActivityThread.java:139)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1307)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5086)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at net.thevgc.quotes.PebbleService.onStartCommand(PebbleService.java:34)
            at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2715)
            at android.app.ActivityThread.access$2100(ActivityThread.java:139)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1307)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5086)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

根据documentation：

intent - ... 如果服务正在重新启动，这可能为 null

因此检查null意图：

public int onStartCommand(Intent intent, int flags, int startId) {
    int cmd = super.onStartCommand(intent, flags, startId);

    if (intent == null) return cmd;

    final String author = intent.getStringExtra("author");
    final String quote = intent.getStringExtra("quote");

    ...
}