我是Android的新手，我试图在播放音频时运行搜索栏。
我收到错误＆＃34;无法启动活动ComponentInfo：java.lang.NullPointerException＆＃34;当我尝试使用＆＃34; setMax＆＃34;。
设置进度条的范围时这是我的代码：
public class PlayerActivity extends Activity {
private MediaPlayer mPlayer;
private SeekBar mSeekBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_player);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
initVariables();
}
public void initVariables(){
mPlayer = new MediaPlayer();
mPlayer = MediaPlayer.create(this, R.raw.raunchy);
mPlayer.setOnCompletionListener(onCompletion);
mSeekBar = (SeekBar) findViewById(R.id.seekBar1);
mSeekBar.setMax(mPlayer.getDuration());
}
private MediaPlayer.OnCompletionListener onCompletion = new MediaPlayer.OnCompletionListener() {
@Override
public void onCompletion(MediaPlayer mPlayer) {
mPlayer.release();
Log.d("FINAL", "CORRECTO");
}
};
public void playOrPause(View v) {
if (!mPlayer.isPlaying()) {
mPlayer.start();
} else {
mPlayer.pause();
}
mHandler.postDelayed(mRunnable, 100);
}
private Handler mHandler = new Handler();
private Runnable mRunnable = new Runnable() {
@Override
public void run() {
mSeekBar.setMax(mPlayer.getDuration());
if(mPlayer.isPlaying()){
int mCurrentPosition = mPlayer.getCurrentPosition() / 1000;
mSeekBar.setProgress(mCurrentPosition);
}
mHandler.postDelayed(this, 1000);
}
};
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_player,
container, false);
return rootView;
}
}
}
这是我的片段。
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.jgutierrezgil.bmusic.MainActivity$PlaceholderFragment" >
<Button
android:id="@+id/button_play"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:text="@string/play_button"
android:onClick="playOrPause" />
<Button
android:id="@+id/button_stop"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_toRightOf="@+id/button_play"
android:text="@string/stop_button"
android:onClick="stop" />
<Button
android:id="@+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_toLeftOf="@+id/button_play"
android:text="Button" />
<SeekBar
android:id="@+id/seekBar1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_above="@+id/button_play"
android:layout_centerHorizontal="true"
android:layout_marginBottom="14dp" />
<TextView
android:id="@+id/startTimeField"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/button1"
android:layout_alignLeft="@+id/seekBar1"
android:text="Small Text"
android:textAppearance="?android:attr/textAppearanceSmall" />
<TextView
android:id="@+id/endTimeField"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/button_stop"
android:layout_alignRight="@+id/seekBar1"
android:text="Small Text"
android:textAppearance="?android:attr/textAppearanceSmall" />
<Button
android:id="@+id/library"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/Player"
android:layout_alignBottom="@+id/Player"
android:layout_alignRight="@+id/seekBar1"
android:layout_toRightOf="@+id/button_play"
android:text="@string/library_button"
android:onClick="toLibrary" />
<Button
android:id="@+id/Player"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/seekBar1"
android:layout_alignParentTop="true"
android:layout_toLeftOf="@+id/button_play"
android:clickable="false"
android:focusable="false"
android:longClickable="false"
android:text="@string/player_button" />
这就是Logcat。
06-03 22:04:47.023: E/AndroidRuntime(1191): FATAL EXCEPTION: main
06-03 22:04:47.023: E/AndroidRuntime(1191): Process: com.jgutierrezgil.bmusic, PID: 1191
06-03 22:04:47.023: E/AndroidRuntime(1191): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jgutierrezgil.bmusic/com.jgutierrezgil.bmusic.PlayerActivity}: java.lang.NullPointerException
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.app.ActivityThread.access$800(ActivityThread.java:135)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.os.Handler.dispatchMessage(Handler.java:102)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.os.Looper.loop(Looper.java:136)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.app.ActivityThread.main(ActivityThread.java:5017)
06-03 22:04:47.023: E/AndroidRuntime(1191): at java.lang.reflect.Method.invokeNative(Native Method)
06-03 22:04:47.023: E/AndroidRuntime(1191): at java.lang.reflect.Method.invoke(Method.java:515)
06-03 22:04:47.023: E/AndroidRuntime(1191): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
06-03 22:04:47.023: E/AndroidRuntime(1191): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
06-03 22:04:47.023: E/AndroidRuntime(1191): at dalvik.system.NativeStart.main(Native Method)
06-03 22:04:47.023: E/AndroidRuntime(1191): Caused by: java.lang.NullPointerException
06-03 22:04:47.023: E/AndroidRuntime(1191): at com.jgutierrezgil.bmusic.PlayerActivity.initVariables(PlayerActivity.java:41)
06-03 22:04:47.023: E/AndroidRuntime(1191): at com.jgutierrezgil.bmusic.PlayerActivity.onCreate(PlayerActivity.java:32)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.app.Activity.performCreate(Activity.java:5231)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
06-03 22:04:47.023: E/AndroidRuntime(1191): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
06-03 22:04:47.023: E/AndroidRuntime(1191): ... 11 more
06-03 22:04:49.193: I/Process(1191): Sending signal. PID: 1191 SIG: 9
清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.jgutierrezgil.bmusic"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="15"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.jgutierrezgil.bmusic.PlayerActivity"
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>
提前感谢您的帮助。
答案 0 :(得分：0)
您使用事务添加片段，然后您会立即尝试在视图层次结构中查找搜索栏视图。未找到seekbar，因此为null，因此在调用setMax时会出现NullPointerException。
您应该从PlayerActivity.onCreate（）中删除这两行：
mSeekBar = (SeekBar) findViewById(R.id.seekBar1);
mSeekBar.setMax(mPlayer.getDuration());
并且在膨胀rootView之后将它们放在PlaceholderFragment.onCreateView（）中，因此您知道将找到搜索条，如下所示：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_player,
container, false);
mSeekBar = (SeekBar) rootView.findViewById(R.id.seekBar1);
mSeekBar.setMax(mPlayer.getDuration());
return rootView;
}