Question

我已经为特定时间编写了警报电话代码，警报将在此期间停止。我已经尝试在模拟器中运行此代码，一切运行顺利。但是当我尝试使用HTC Desire HD（Android 2.3.5）时，应用程序会被强制关闭。有人能告诉我发生了什么吗？

public class RingerActivity extends Activity{
/** Called when the activity is first created. */
Button press;
boolean tone = true;
MediaPlayer mp;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mp = new MediaPlayer();
    mp = MediaPlayer.create(RingerActivity.this, R.raw.alarm);
    try {
        mp.prepare();

    } catch (IllegalStateException e) {
        e.printStackTrace();
    } catch (Exception e) {
        Toast.makeText(this, e.getMessage() , Toast.LENGTH_SHORT).show();         }
    mp.start();

    Handler h = new Handler();
    Runnable stopPlaybackRun = new Runnable() {
        public void run(){
            mp.stop();
            mp.release();
        }    
    };
    h.postDelayed(stopPlaybackRun, 20 * 1000);

    AudioManager manager = (AudioManager)getSystemService(AUDIO_SERVICE);
    manager.setRingerMode(AudioManager.RINGER_MODE_NORMAL);
    int maxVolume = manager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
    manager.setStreamVolume(AudioManager.STREAM_MUSIC, maxVolume, 0);

}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event){

    if (keyCode == KeyEvent.KEYCODE_VOLUME_UP){
        Toast.makeText(this, "Volume Up", Toast.LENGTH_LONG).show();
        return true;
    }

    if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN){
        Toast.makeText(this, "Volume Down", Toast.LENGTH_LONG).show();
        return true;
    }

    return super.onKeyDown(keyCode, event);
}

logcat的

11-09 13:36:51.220: E/AndroidRuntime(2370): FATAL EXCEPTION: main
11-09 13:36:51.220: E/AndroidRuntime(2370): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.testing.ringer/com.testing.ringer.RingerActivity}: java.lang.NullPointerException
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1872)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1893)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.app.ActivityThread.access$1500(ActivityThread.java:135)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1054)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.os.Handler.dispatchMessage(Handler.java:99)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.os.Looper.loop(Looper.java:150)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.app.ActivityThread.main(ActivityThread.java:4385)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at java.lang.reflect.Method.invokeNative(Native Method)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at java.lang.reflect.Method.invoke(Method.java:507)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at dalvik.system.NativeStart.main(Native Method)
11-09 13:36:51.220: E/AndroidRuntime(2370): Caused by: java.lang.NullPointerException
11-09 13:36:51.220: E/AndroidRuntime(2370):     at com.testing.ringer.RingerActivity.onCreate(RingerActivity.java:35)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
11-09 13:36:51.220: E/AndroidRuntime(2370):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1836)
11-09 13:36:51.220: E/AndroidRuntime(2370):     ... 11 more

清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.testing.ringer"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk android:minSdkVersion="10" />

<uses-permission android:name="android.permission.RECORD_AUDIO"/>

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
    <activity
        android:name=".RingerActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

</manifest>

Answer 1

问题是由onCreate上的空指针异常引起的。有时音频服务没有返回AudioManager。

更改代码：

AudioManager manager = (AudioManager)getSystemService(AUDIO_SERVICE);
manager.setRingerMode(AudioManager.RINGER_MODE_NORMAL);
int maxVolume = manager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
manager.setStreamVolume(AudioManager.STREAM_MUSIC, maxVolume, 0);

如下所示onCreate：

AudioManager manager = (AudioManager)getSystemService(AUDIO_SERVICE);
if(manager!=null){
manager.setRingerMode(AudioManager.RINGER_MODE_NORMAL);
int maxVolume = manager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
manager.setStreamVolume(AudioManager.STREAM_MUSIC, maxVolume, 0);
}

Answer 2

尝试使用此代码，

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mp = MediaPlayer.create(RingerActivity.this, R.raw.alarm);
    // are you sure that res/raw/alarm is a valid media file?
    mp.start();

Answer 3

您的活动中第35行有一个NullPointerException。解决它。

Answer 4

MediaPlayer mp = MediaPlayer.create(context, R.raw.alarm);
mp.prepare(); <- Error, delete this line in your code

您无需调用方法＆＃34; prepare（）;＆＃34;，方法＆＃34;创建（，）;＆＃34;为你这样做。：）

如何解决错误“无法启动活动ComponentInfo”？

4 个答案: