Android首选项示例

Android共享首选项被用于存储和检索基本信息。在Android中，字符串、整数、长整数、数字等被视为基本数据类型。

Android共享首选项被用于以键值对的方式存储数据，以便我们可以根据键检索值。

它被广泛用于获取用户的信息，例如在设置中。

Android首选项示例

让我们看一个简单的Android共享首选项示例。

activity_main.xml

从工具箱中拖动一个Textview和两个按钮。

<?xml version="1.0" encoding="utf-8"?>  
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:app="http://schemas.android.com/apk/res-auto"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    tools:context="example.javatpoint.com.preferences.MainActivity">  

    <TextView  
        android:id="@+id/txtPrefs"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_centerVertical="true"  
        android:text="Data:" />  

    <Button  
        android:id="@+id/storeinformation"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_below="@+id/showinformation"  
        android:layout_centerHorizontal="true"  
        android:layout_marginTop="18dp"  
        android:text="Store Information" />  

    <Button  
        android:id="@+id/showinformation"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_alignParentTop="true"  
        android:layout_centerHorizontal="true"  
        android:layout_marginTop="17dp"  
        android:text="Show Information" />  

</RelativeLayout>  

array.xml

它被创建在res/values目录下。

<?xml version="1.0" encoding="utf-8"?>  
<resources>  
    <string-array name="listOptions">  
        <item>English</item>  
        <item>Hindi</item>  
        <item>Other</item>  
    </string-array>  

    <string-array name="listValues">  
        <item>English Language</item>  
        <item>Hindi Language</item>  
        <item>Other Language</item>  
    </string-array>  
</resources>  

prefs.xml

它在res/xml目录中创建。

<?xml version="1.0" encoding="utf-8"?>  
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">  
    <PreferenceCategory  
        android:summary="Username and password information"  
        android:title="Login information" >  
        <EditTextPreference  
            android:key="username"  
            android:summary="Please enter your login username"  
            android:title="Username" />  
        <EditTextPreference  
            android:key="password"  
            android:summary="Enter your password"  
            android:title="Password" />  
    </PreferenceCategory>  

    <PreferenceCategory  
        android:summary="Username and password information"  
        android:title="Settings" >  
        <CheckBoxPreference  
            android:key="checkBox"  
            android:summary="On/Off"  
            android:title="Keep me logged in" />  

        <ListPreference  
            android:entries="@array/listOptions"  
            android:entryValues="@array/listValues"  
            android:key="listpref"  
            android:summary="List preference example"  
            android:title="List preference" />  
    </PreferenceCategory>  
</PreferenceScreen>  

主要Activity类

package example.javatpoint.com.preferences;

import android.content.Intent;
import android.content.SharedPreferences;
import android.preference.PreferenceManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button storeinformation = (Button) findViewById(R.id.storeinformation);
        Button showinformation = (Button) findViewById(R.id.showinformation);
        textView = (TextView) findViewById(R.id.txtPrefs);

        View.OnClickListener listener = new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch (v.getId()) {
                    case R.id.storeinformation:
                        Intent intent = new Intent(MainActivity.this,PrefsActivity.class);
                        startActivity(intent);
                        break;
                    case R.id.showinformation:
                        displaySharedPreferences();
                        break;
                    default:
                        break;
                }
            }
        };
        storeinformation.setOnClickListener(listener);
        showinformation.setOnClickListener(listener);
    }


    private void displaySharedPreferences() {
        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(MainActivity.this);
        String username = prefs.getString("username", "Default NickName");
        String passw = prefs.getString("password", "Default Password");
        boolean checkBox = prefs.getBoolean("checkBox", false);
        String listPrefs = prefs.getString("listpref", "Default list prefs");


        StringBuilder builder = new StringBuilder();
        builder.append("Username: " + username + "\n");
        builder.append("Password: " + passw + "\n");
        builder.append("Keep me logged in: " + String.valueOf(checkBox) + "\n");
        builder.append("List preference: " + listPrefs);
        textView.setText(builder.toString());

    }

}
``````

#### PrefsActivity类
```java 
package example.javatpoint.com.preferences;

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

public class PrefsActivity extends PreferenceActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.prefs);
    }
}
``````

#### AndroidManifest.xml
```xml
<?xml version="1.0" encoding="utf-8"?>  
<manifest xmlns:android="http://schemas.android.com/apk/res/android"  
    package="example.javatpoint.com.preferences">  

    <application  
        android:allowBackup="true"  
        android:icon="@mipmap/ic_launcher"  
        android:label="@string/app_name"  
        android:roundIcon="@mipmap/ic_launcher_round"  
        android:supportsRtl="true"  
        android:theme="@style/AppTheme">  
        <activity android:name=".MainActivity">  
            <intent-filter>  
                <action android:name="android.intent.action.MAIN" />  

                <category android:name="android.intent.category.LAUNCHER" />  
            </intent-filter>  
        </activity>  
        <activity  android:name=".PrefsActivity"  
            android:theme="@android:style/Theme.Black.NoTitleBar" >  
        </activity>  
    </application>  

</manifest>  

输出：