Question

如何为首选项中的搜索栏设置OnChangeListener（图片http://img825.imageshack.us/img825/6729/prefscreen.png）？我已经尝试过这段代码，但它将返回空指针异常：

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>

搜索栏的布局：

<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>

日志：

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

我遇到了同样的NPE问题，我通过定义我的SeekbarPreference得到了它并在onBindDialogView中注册了监听器。这是代码：

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) {
    }
}

这是我的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>

我希望它有所帮助！

如何为首选项中的seekBar设置onChangeListener？

1 个答案: