android - 单击设置按钮时出错

Question

我是 Android 开发的新手，正试图让设置菜单显示在我的应用程序上。

首选项的 XML 文件在这里:

<?xml version="1.0" encoding="UTF-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
android:title="@string/settings">
<SwitchPreference
    android:title="Switch Preference"
    android:key="switchpref"
    android:switchTextOn="ON"
    android:switchTextOff="OFF"
    android:summary="Night Mode"
    android:defaultValue="false"
    android:disableDependentsState="false"
    />

 </PreferenceScreen>

主类文件在这里，我尝试切换到设置 Activity

package com.example.notepad;

import java.util.zip.Inflater;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class HomeScreen extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home_screen);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_home_screen, menu);
    return true;
}

public boolean onOptionsItemSelected(MenuItem item) {
    switch(item.getItemId())
    {
    case R.id.menu_settings:
         Intent intent = new Intent(HomeScreen.this,      PreferencesFragment.class);
            startActivity(intent);
            return true;

            default:
                return super.onOptionsItemSelected(item);
    }

}
}

显示设置菜单的 Preferences Java 文件在这里

package com.example.notepad;

import android.app.Activity;
import android.os.Bundle;

public class PreferencesFragment extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.xml.preferences);
}

}

我不明白为什么会发生错误。当我单击“设置”按钮时，它只显示通用的“不幸的是，应用程序已停止”

日志文件在这里

01-17 19:49:28.795: E/AndroidRuntime(756): FATAL EXCEPTION: main
01-17 19:49:28.795: E/AndroidRuntime(756): java.lang.RuntimeException: Unable to start    activity ComponentInfo{com.example.notepad/com.example.notepad.PreferencesFragment}:  android.view.InflateException: Binary XML file line #2: Error inflating class  PreferenceScreen
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.os.Looper.loop(Looper.java:137)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.ActivityThread.main(ActivityThread.java:4745)
 01-17 19:49:28.795: E/AndroidRuntime(756):     at java.lang.reflect.Method.invokeNative(Native Method)
01-17 19:49:28.795: E/AndroidRuntime(756):  at java.lang.reflect.Method.invoke(Method.java:511)
01-17 19:49:28.795: E/AndroidRuntime(756):  at      com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-17 19:49:28.795: E/AndroidRuntime(756):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-17 19:49:28.795: E/AndroidRuntime(756):  at dalvik.system.NativeStart.main(Native Method)
01-17 19:49:28.795: E/AndroidRuntime(756): Caused by: android.view.InflateException: Binary XML file line #2: Error inflating class PreferenceScreen
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:698)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.view.LayoutInflater.inflate(LayoutInflater.java:466)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.view.LayoutInflater.inflate(LayoutInflater.java:396)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.view.LayoutInflater.inflate(LayoutInflater.java:352)
01-17 19:49:28.795: E/AndroidRuntime(756):  at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:256)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.Activity.setContentView(Activity.java:1867)
01-17 19:49:28.795: E/AndroidRuntime(756):  at com.example.notepad.PreferencesFragment.onCreate(PreferencesFragment.java:12)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.Activity.performCreate(Activity.java:5008)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
01-17 19:49:28.795: E/AndroidRuntime(756):  ... 11 more
01-17 19:49:28.795: E/AndroidRuntime(756): Caused by: java.lang.ClassNotFoundException: android.view.PreferenceScreen
01-17 19:49:28.795: E/AndroidRuntime(756):  at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
01-17 19:49:28.795: E/AndroidRuntime(756):  at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
 01-17 19:49:28.795: E/AndroidRuntime(756):     at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.view.LayoutInflater.createView(LayoutInflater.java:552)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.view.LayoutInflater.onCreateView(LayoutInflater.java:643)
01-17 19:49:28.795: E/AndroidRuntime(756):  at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:66)
01-17 19:49:28.795: E/AndroidRuntime(756):  at android.view.LayoutInflater.onCreateView(LayoutInflater.java:660)
01-17 19:49:28.795: E/AndroidRuntime(756):  at          android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:685)
01-17 19:49:28.795: E/AndroidRuntime(756):  ... 20 more

编辑 - 我的 AndroidManifest.xml 文件:

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

<uses-sdk
    android:minSdkVersion="14"
    android:targetSdkVersion="16" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.notepad.HomeScreen"
        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=".PreferencesFragment" />
</application>

Answer 1

您不能在 Activity 中使用 PreferenceScreen(PreferencesFragment 扩展 Activity)。阅读文档并正确使用它。

PreferenceScreen can appear in two places:

When a PreferenceActivity points to this, it is used as the root and is not shown (only the contained preferences are shown).

When it appears inside another preference hierarchy, it is shown and serves as the gateway to another screen of preferences (either by showing another screen of preferences as a Dialog or via a startActivity(android.content.Intent) from the getIntent()). The children of this PreferenceScreen are NOT shown in the screen that this PreferenceScreen is shown in. Instead, a separate screen will be shown when this preference is clicked.