Android SharedPreferences 没有改变

Question

所以我正在了解 SharedPreferences在 Android 中。

我想我会很快尝试模拟一些简单的东西。当用户从选项列表中选择一个特定选项时(在本例中为 3 个选项)- 布局文件将相应更改。 However, it always assumes the default value supplied, hence never changes the layout when another option is selected - so when another option is selected, it is recorded fine, but the layout doesn't change, this leads me to believe that there is perhaps首先获得偏好时出现问题，我想知道是否有人可以快速查看并发现一些明显的东西，或者根据他们的经验/智慧发现一些不那么明显的东西 - 这是代码:

主要 Activity .java:

package com.example.preferenceslayout;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends Activity
    implements OnSharedPreferenceChangeListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        loadPreferences();
    }

    @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;
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        switch(item.getItemId()) {
        case R.id.preferences:
            startActivity(new Intent(getApplicationContext(),
                     AppPreferences.class));
            break;
        }
        return false;
    }

    public void loadPreferences() {
        SharedPreferences prefs = getApplicationContext().
            getSharedPreferences("mode", MODE_PRIVATE);
        int layoutPref = prefs.getInt("mode", 10);
        switch(layoutPref) {
        case 10:
            setContentView(R.layout.activity_main);
            break;
        case 20:
            setContentView(R.layout.second_layout);
            break;
        case 30:
            setContentView(R.layout.third_layout);
            break;
        }
        prefs.registerOnSharedPreferenceChangeListener(MainActivity.this);
    }

    @Override
    public void onSharedPreferenceChanged(SharedPreferences arg0, String arg1) {
        loadPreferences();      
    }
}

首选项.xml:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >
    <ListPreference
        android:key="mode"
        android:title="@string/mode"
        android:defaultValue="1"
        android:summary="@string/summary"
        android:entries="@array/listArray"
        android:entryValues="@array/listValues" />
</PreferenceScreen>

AppPreferences.xml:

package com.example.preferenceslayout;

import android.os.Bundle;
import android.preference.PreferenceActivity;

public class AppPreferences extends PreferenceActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preference);
    }
}

主.xml:

<menu xmlns:android="http://schemas.android.com/apk/res/android" >
    <item
        android:id="@+id/action_settings"
        android:orderInCategory="100"
        android:showAsAction="never"
        android:title="@string/action_settings"/>
    <item
        android:id="@+id/preferences"
        android:title="Preferences" />
</menu>

PreferencesLayoutManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.preferenceslayout"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.preferenceslayout.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name="com.example.preferenceslayout.AppPreferences">
            <intent-filter>
                <action android:name=".AppPreferences" />
            </intent-filter>
        </activity>
    </application>
</manifest>

数组.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="listArray">
        <item>10</item>
        <item>20</item>
        <item>30</item>
    </string-array>
    <string-array name="listValues">
        <item>1</item>
        <item>2</item>
    </string-array>
</resources>

Answer 1

您永远不会写您的喜好。你需要一个 prefs.putInt("mode", some_int); 某处。此外，您的听众毫无用处 - 放弃它。

您正在写入默认共享首选项，因为首选项屏幕在那里写入。 “模式”只是关键——默认共享首选项中有一个键，你的首选项文件(名为“mode_something.xml”)中有一个键——但是你写了一个(自动通过首选项屏幕)，你读了另一个(永远不会设置)