下面的代码在Eclipse的模拟器中运行顺畅,但是当我在Android手机和平板电脑上运行它时会出现问题。
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);
//Error occurs at here
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);
if(manager!=null){
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);
}
我在“mp.start()”行中得到一个“NullPointException”。我一直在研究这个问题,但我真的不知道发生了什么,我在我的Android智能手机和平板电脑(Gingerbread和ICS)上尝试了这个,但app力量关闭了。我需要你们的帮助......谢谢......
logcat的
11-09 15:41:09.909: E/AndroidRuntime(11975): FATAL EXCEPTION: main
11-09 15:41:09.909: E/AndroidRuntime(11975): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.testing.ringer/com.testing.ringer.RingerActivity}: java.lang.NullPointerException
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1872)
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1893)
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.app.ActivityThread.access$1500(ActivityThread.java:135)
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1054)
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.os.Handler.dispatchMessage(Handler.java:99)
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.os.Looper.loop(Looper.java:150)
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.app.ActivityThread.main(ActivityThread.java:4385)
11-09 15:41:09.909: E/AndroidRuntime(11975): at java.lang.reflect.Method.invokeNative(Native Method)
11-09 15:41:09.909: E/AndroidRuntime(11975): at java.lang.reflect.Method.invoke(Method.java:507)
11-09 15:41:09.909: E/AndroidRuntime(11975): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
11-09 15:41:09.909: E/AndroidRuntime(11975): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
11-09 15:41:09.909: E/AndroidRuntime(11975): at dalvik.system.NativeStart.main(Native Method)
11-09 15:41:09.909: E/AndroidRuntime(11975): Caused by: java.lang.NullPointerException
11-09 15:41:09.909: E/AndroidRuntime(11975): at com.testing.ringer.RingerActivity.onCreate(RingerActivity.java:23)
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
11-09 15:41:09.909: E/AndroidRuntime(11975): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1836)
11-09 15:41:09.909: E/AndroidRuntime(11975): ... 11 more
Ringer Manifest
<?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>
答案 0 :(得分:4)
NullPointerException意味着mp为null。这意味着MediaPlayer.create()失败。 R.raw.alarm存在吗?
答案 1 :(得分:1)
NullPointerException,因为当没有要使用的实例或数组时,最好跟踪到put breakpoint and debug your code
。
看起来您的代码很完美,只需确定.mp3
是否存在?并且你完全保留在raw
文件夹中。
最后尝试卸载现有的,然后清理项目并运行。祝你好运。
答案 2 :(得分:1)
你有没有尝试清理项目? 只有在清理项目后,才会在包浏览器中显示新添加的资源。