java.lang.NullPointerException 致命异常 : IntentService[GCMIntentService-876799952849-1]

Question

请在将其标记为重复之前完整阅读我的问题，我已经彻底搜索了这种情况。我目前正在开发一个通过网站远程控制您的 Android 设备的 Android 应用程序。目前，当我我正在尝试发送命令来启动录音机。我创建了一个名为audiorecorder.java的类，当消息“startrecorder”从服务器端到达时创建其对象。该消息实际上在 gcmintent service.java 中进行比较。我是粘贴代码 fragment 以及 logcat。请帮助我，因为这个错误不仅出现在录音机功能的 acse 中，而且在其他情况下也出现，例如拍摄 scrrenshot 或从相机拍照。提前致谢。

录音机.java

package com.androidhive.pushnotifications;

import java.io.File;

import java.io.IOException;

import android.media.MediaPlayer;
import android.media.MediaRecorder;
import android.os.Environment;

import android.app.Activity;

public class AudioRecorder extends Activity {
    final MediaRecorder recorder = new MediaRecorder();
    public String path;

    public void onCreate(String path) {
        this.path = sanitizePath(path);
    }

    private String sanitizePath(String path) {
        if (!path.startsWith("/")) {
            path = "/" + path;
        }
        if (!path.contains(".")) {
            path += ".3gp";
        }
        return Environment.getExternalStorageDirectory().getAbsolutePath()
                + path;
    }

    public void start() throws IOException {
        String state = android.os.Environment.getExternalStorageState();
        if (!state.equals(android.os.Environment.MEDIA_MOUNTED)) {
            throw new IOException("SD Card is not mounted.  It is " + state
                    + ".");
        }

        // make sure the directory we plan to store the recording in exists
        File directory = new File(path).getParentFile();
        if (!directory.exists() && !directory.mkdirs()) {
            throw new IOException("Path to file could not be created.");
        }

        recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
        recorder.setOutputFile(path);
        recorder.prepare();
        recorder.start();
    }

    public void stop() throws IOException {
        recorder.stop();
        recorder.release();
    }

    public void playrecording(String path) throws IOException {
        MediaPlayer mp = new MediaPlayer();
        mp.setDataSource(path);
        mp.prepare();
        mp.start();
        mp.setVolume(10, 10);
    }

}   





Gcmintentservice.java --->
 else if(message.equalsIgnoreCase ("startrecorder")){

            AudioRecorder a = new AudioRecorder();
            try {
                a.start();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }




Logcat:

    11-23 11:36:11.338: D/dalvikvm(2313): GC_EXTERNAL_ALLOC freed 51K, 51% free 2687K/5379K, external 0K/0K, paused 362ms
    11-23 11:36:11.438: D/dalvikvm(2313): GC_EXTERNAL_ALLOC freed 1K, 51% free 2688K/5379K, external 0K/512K, paused 88ms
    11-23 11:36:18.685: V/GCMBroadcastReceiver(2313): onReceive: com.google.android.c2dm.intent.RECEIVE
    11-23 11:36:18.695: V/GCMBroadcastReceiver(2313): GCM IntentService class: com.androidhive.pushnotifications.GCMIntentService
    11-23 11:36:18.695: V/GCMBaseIntentService(2313): Acquiring wakelock
    11-23 11:36:18.735: V/GCMBaseIntentService(2313): Intent service name: GCMIntentService-876799952849-1
    11-23 11:36:18.755: I/GCMIntentService(2313): Received message
    11-23 11:36:18.775: V/GCMBaseIntentService(2313): Releasing wakelock
    11-23 11:36:18.775: W/dalvikvm(2313): threadid=10: thread exiting with uncaught exception (group=0x40018560)
    11-23 11:36:18.785: E/AndroidRuntime(2313): FATAL EXCEPTION: IntentService[GCMIntentService-876799952849-1]
    11-23 11:36:18.785: E/AndroidRuntime(2313): java.lang.NullPointerException
    11-23 11:36:18.785: E/AndroidRuntime(2313): at java.io.File.fixSlashes(File.java:205)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at java.io.File.init(File.java:189)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at java.io.File.<init>(File.java:139)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at com.androidhive.pushnotifications.AudioRecorder.start(AudioRecorder.java:39)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at com.androidhive.pushnotifications.GCMIntentService.onMessage(GCMIntentService.java:128)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at com.google.android.gcm.GCMBaseIntentService.onHandleIntent(GCMBaseIntentService.java:223)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:59)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at android.os.Handler.dispatchMessage(Handler.java:99)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at android.os.Looper.loop(Looper.java:130)
    11-23 11:36:18.785: E/AndroidRuntime(2313): at android.os.HandlerThread.run(HandlerThread.java:60)

Answer 1

这看起来不对:

public String path;

public void onCreate(String path) {
    this.path = sanitizePath(path);
}

此 orCreate 没有 noCreate 的签名Activity 的方法，因此启动 Activity 时不会执行该方法。因此，path 保持为空，导致 File directory = new File(path).getParentFile(); 处的 NullPointerException。

如果您希望将 path 变量传递给您的 Activity，您应该将其放入启动 Activity 的 Intent 中。