如何爲偏好設置的seekBar設置onChangeListener？

Question

如何爲偏好設置的seekbar設置OnChangeListener（圖片http://img825.imageshack.us/img825/6729/prefscreen.png）？我已經嘗試過這個代碼，但它會與空指針異常返回：

PreferenceActivity：

import android.os.Bundle; 
import android.preference.Preference; 
import android.preference.PreferenceActivity; 
import android.widget.SeekBar; 

public class peferences extends PreferenceActivity { 
    private SeekBar SensitivitySeekBar; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     addPreferencesFromResource(R.xml.preferences); 

     SensitivitySeekBar = (SeekBar)findViewById(R.id.SeekBar2); 
     SensitivitySeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() { 

      public void onStopTrackingTouch(SeekBar seekBar) { 
       // TODO Auto-generated method stub 

      } 

      public void onStartTrackingTouch(SeekBar seekBar) { 
       // TODO Auto-generated method stub 

      } 

      public void onProgressChanged(SeekBar seekBar, int progress, 
        boolean fromUser) { 
       // TODO Auto-generated method stub 

      } 
     }); 
    } 

的preferences.xml：

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"> 
     <PreferenceCategory 
      android:title="@string/pref_accelerometer_title" 
      android:key="preference_accelerometer" > 
      <CheckBoxPreference 
       android:key="pref_key_x_axis" 
       android:summary="@string/preference_x_axis_summary" 
       android:title="Use x-axis" 
       android:defaultValue="true" android:order="1" android:enabled="true"/> 
      <CheckBoxPreference 
       android:title="Use y-axis" 
       android:key="pref_key_y_axis" 
       android:summary="@string/preference_y_axis_summary" 
       android:order="2" 
       android:enabled="true" 
       android:defaultValue="true"/> 
      <CheckBoxPreference 
       android:summary="@string/preference_z_axis_summary" 
       android:title="Use z-axis" 
       android:key="pref_key_z_axis" 
       android:order="3" 
       android:enabled="true" 
       android:defaultValue="true"/> 
      <CheckBoxPreference 
       android:title="Accelerometer value" 
       android:key="pref_accelerometer_value" 
       android:summary="@string/preference_show_accelerometer_value"/> 
      <Preference 
       android:layout="@layout/seekbar" 
       android:order="4" 
       android:key="seekbar"/> 



      </PreferenceCategory> 

    </PreferenceScreen> 

佈局搜索條：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" > 

    <TextView 
     android:id="@+id/Sensitivity_title" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true" 
     android:layout_alignParentTop="true" 
     android:layout_marginLeft="10dp" 
     android:layout_marginTop="15dp" 
     android:text="@string/preference_sensitivity_title" 
     android:textAppearance="?android:attr/textAppearanceMedium" /> 

    <TextView 
     android:id="@+id/Sensitivity_summary" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignLeft="@+id/Sensitivity_title" 
     android:layout_below="@+id/Sensitivity_title" 
     android:text="@string/preference_sensitivity_summary" /> 

    <SeekBar 
     android:id="@+id/seekBar2" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true" 
     android:layout_below="@+id/Sensitivity_summary" 
     android:max="5000" /> 


</RelativeLayout> 

登錄：

12-26 22:55:35.204: D/dalvikvm(24291): GC_CONCURRENT freed 329K, 4% free 9212K/9572K, paused 4ms+5ms, total 29ms 
12-26 22:55:36.626: D/AndroidRuntime(24291): Shutting down VM 
12-26 22:55:36.626: W/dalvikvm(24291): threadid=1: thread exiting with uncaught exception (group=0x4154e930) 
12-26 22:55:36.634: E/AndroidRuntime(24291): FATAL EXCEPTION: main 
12-26 22:55:36.634: E/AndroidRuntime(24291): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.bluetoothc/com.example.bluetoothc.peferences}: java.lang.NullPointerException 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.os.Handler.dispatchMessage(Handler.java:99) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.os.Looper.loop(Looper.java:137) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.app.ActivityThread.main(ActivityThread.java:5039) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at java.lang.reflect.Method.invokeNative(Native Method) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at java.lang.reflect.Method.invoke(Method.java:511) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at dalvik.system.NativeStart.main(Native Method) 
12-26 22:55:36.634: E/AndroidRuntime(24291): Caused by: java.lang.NullPointerException 
12-26 22:55:36.634: E/AndroidRuntime(24291): at com.example.bluetoothc.peferences.onCreate(peferences.java:23) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.app.Activity.performCreate(Activity.java:5104) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
12-26 22:55:36.634: E/AndroidRuntime(24291): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
12-26 22:55:36.634: E/AndroidRuntime(24291): ... 11 more 
12-26 22:55:39.001: I/Process(24291): Sending signal. PID: 24291 SIG: 9 

Answer 1

我遇到了同樣的NPE問題，我通過定義我的SeekbarPreference並在onBindDialogView中註冊了監聽器。下面是代碼：

public class SeekbarPreference extends DialogPreference implements 
     OnSeekBarChangeListener { 

    private SeekBar mSeekbar; 

    @Override 
    protected void onBindDialogView(View view) { 
     super.onBindDialogView(view); 

     mSeekbar = (SeekBar) view.findViewById(R.id.sb_text_size); 
     mSeekbar.setOnSeekBarChangeListener(this); 
    } 

    public SeekbarPreference(Context context, AttributeSet attrs) { 
     super(context, attrs); 
     this.setDialogLayoutResource(R.layout.setting_textsize_seekbar); 
    } 

    @Override 
    protected void onDialogClosed(boolean positiveResult) { 
     if (positiveResult) { 
      // save to SharedPrefs, etc 
     } 
    } 

    @Override 
    public void onProgressChanged(SeekBar seekbar, int progress, boolean fromUser) { 
    } 

    @Override 
    public void onStartTrackingTouch(SeekBar seekBar) { 
    } 

    @Override 
    public void onStopTrackingTouch(SeekBar seekBar) { 
    } 
} 

這裏是我的preference.xml：

<PreferenceCategory 
    <com.flounder.xeniaNote.view.SeekbarPreference 
     android:dialogLayout="@layout/setting_textsize_seekbar" 
     android:key="@string/pref_text_size_key" 
     android:title="@string/pref_text_size" /> 

    ... 
</PreferenceCategory> 

我希望它能幫助！