从XML创建DialogPreference

Question

我一直试图使用android.preference.DialogPreference从XML中膨胀,但文档似乎缺少一些基本的部分,我无法在任何地方找到一个有效的例子.我的XML现在看起来像这样(我尝试了许多排列,但这似乎是一个合理的最小值):

<DialogPreference
android:key="funThing" android:title="Fun Thing"
android:dialogLayout="@layout/fun_layout"
android:positiveButtonText="OK"
android:negativeButtonText="Cancel"
/>

我在这一点上的假设是它需要子类DialogPreference而不是直接使用它.首先,我找不到将实际偏好值与对话框本身中的元素相关联的方法,这在反射时是一种赠品.而且,看来源DialogPreference.java似乎也证实了这一点.我还注意到官方文档将其称为"基类".但至少,在网上建立一个确定性足够的来源会很有帮助,这将有助于下一个N人比我更快地解决这个问题.

对于记录,日志文件如下所示:

I/ActivityManager(   61): Starting: Intent { cmp=org.jeremy.android/.PreferencesActivity } from pid 2755
W/Resources( 2755): Converting to string: TypedValue{t=0x10/d=0x4b0 a=-1}
W/Resources( 2755): Converting to string: TypedValue{t=0x10/d=0x20 a=-1}
D/AndroidRuntime( 2755): Shutting down VM
W/dalvikvm( 2755): threadid=1: thread exiting with uncaught exception (group=0x40015560)
E/AndroidRuntime( 2755): FATAL EXCEPTION: main
E/AndroidRuntime( 2755): java.lang.RuntimeException: Unable to start activity ComponentInfo{org.jeremy.android/org.jeremy.android.PreferencesActivity}: android.view.InflateException: Binary XML file line #28: Error inflating class java.lang.reflect.Constructor
E/AndroidRuntime( 2755):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
E/AndroidRuntime( 2755):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
E/AndroidRuntime( 2755):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
E/AndroidRuntime( 2755):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
E/AndroidRuntime( 2755):    at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime( 2755):    at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime( 2755):    at android.app.ActivityThread.main(ActivityThread.java:3683)
E/AndroidRuntime( 2755):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 2755):    at java.lang.reflect.Method.invoke(Method.java:507)
E/AndroidRuntime( 2755):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
E/AndroidRuntime( 2755):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
E/AndroidRuntime( 2755):    at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime( 2755): Caused by: android.view.InflateException: Binary XML file line #28: Error inflating class java.lang.reflect.Constructor
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.createItem(GenericInflater.java:397)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.onCreateItem(GenericInflater.java:417)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.createItemFromTag(GenericInflater.java:428)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.rInflate(GenericInflater.java:481)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.rInflate(GenericInflater.java:493)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.inflate(GenericInflater.java:326)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.inflate(GenericInflater.java:263)
E/AndroidRuntime( 2755):    at android.preference.PreferenceManager.inflateFromResource(PreferenceManager.java:251)
E/AndroidRuntime( 2755):    at android.preference.PreferenceActivity.addPreferencesFromResource(PreferenceActivity.java:262)
E/AndroidRuntime( 2755):    at org.jeremy.android.PreferencesActivity.onCreate(PreferencesActivity.java:40)
E/AndroidRuntime( 2755):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
E/AndroidRuntime( 2755):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
E/AndroidRuntime( 2755):    ... 11 more
E/AndroidRuntime( 2755): Caused by: java.lang.InstantiationException: android.preference.DialogPreference
E/AndroidRuntime( 2755):    at java.lang.reflect.Constructor.constructNative(Native Method)
E/AndroidRuntime( 2755):    at java.lang.reflect.Constructor.newInstance(Constructor.java:415)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.createItem(GenericInflater.java:383)
E/AndroidRuntime( 2755):    ... 22 more
W/ActivityManager(   61):   Force finishing activity org.jeremy.android/.PreferencesActivity
W/ActivityManager(   61):   Force finishing activity org.jeremy.android/.SplashActivity

Answer 1

下面是一个如何使用对话框首选项的示例(如您所提到的子类化).

package dk.myapp.views;

import android.content.Context;
import android.preference.DialogPreference;
import android.util.AttributeSet;

/**
 * The OptionDialogPreference will display a dialog, and will persist the
 * <code>true</code> when pressing the positive button and <code>false</code>
 * otherwise. It will persist to the android:key specified in xml-preference.
 */
public class OptionDialogPreference extends DialogPreference {

    public OptionDialogPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected void onDialogClosed(boolean positiveResult) {
        super.onDialogClosed(positiveResult);
        persistBoolean(positiveResult);
    }

}

preferences.xml应该包含

<dk.myapp.views.OptionDialogPreference
            android:key="@string/prefKeyResetQuests"
            android:dialogIcon="@android:drawable/ic_dialog_alert"
            android:title="Reset Quests"
            android:summary="Reset all quest-progress."
            android:dialogMessage="Are you sure you wish to reset your quest progress? This action cannot be undone!"
            android:positiveButtonText="Clear Quests"
            android:negativeButtonText="Cancel"/>

我有一个res/value包含(虽然键名也可以在上面明确声明).

<string name="prefKeyResetQuests">resetQuests</string>  

我的PreferenceActivity从onPause实际重置.请注意,onStop可能为时已晚,因为在按下后不会立即调用onStop:

@Override
public void onPause() {
    SharedPreferences prefs = android.preference.PreferenceManager.
        getDefaultSharedPreferences(getBaseContext());
    if(prefs.getBoolean(
        getResources().getString(R.string.prefKeyResetQuests), false)) {
        // apply reset, and then set the pref-value back to false
    }
}

或者等效,因为我们仍然在PreferenceActivity中:

@Override
protected void onPause() {
    Preference prefResetQuests =
        findPreference(getResources().getString(R.string.prefKeyResetQuests));
    if(prefResetQuests.getSharedPreferences().
        getBoolean(prefResetQuests.getKey(), false)){
        // apply reset, and then set the pref-value back to false 
    }
}

Answer 2

这个很奇怪,你需要子类DialogPreference.子类不需要做任何事情.所以

public class MyDialogPreference extends DialogPreference {

    public MyDialogPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
    }

} 

可以实例化.虽然老飞机DialogPreference不能.非常奇怪,它们应该完全相同.

Answer 3

第一:

创建自己的类,DialogPreference如下所示:

package com.test.view;

import android.preference.DialogPreference;

public class DialogExPreference extends DialogPreference 
{
    public DialogExPreference(Context oContext, AttributeSet attrs)
    {
        super(oContext, attrs);     
    }
}

第二:

修改xml文件如下:

<PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android">

    <com.test.view.DialogExPreference
        android:title="@string/title"
        android:dialogMessage="@string/lite"              
                android:negativeButtonText="test"/> 

</PreferenceScreen>

那没关系.