SharedPreferences类的使用

Posted 2021-11-25 neowu

SharedPreferences，用xml文件保存用户的偏好设置，是一个轻量级的存储类。

demo效果：

 

代码:

activity_main

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

</LinearLayout>

 

 

activity_settings

<?xml version="1.0" encoding="utf-8"?>

    <fragment
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:name="com.example.admin.sharedpreferences.SettingsActivity$preferenceFragment"
        android:id="@+id/preference"/>

menu.menu

 

<?xml version="1.0" encoding="utf-8"?>
<menu
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/menu_settings"
        android:title="settings"
        app:showAsAction="never"/>

</menu>

 

 

arrays

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="color_show">
        <item>black</item>
        <item>red</item>
        <item>blue</item>
        <item>green</item>
    </string-array>

</resources>

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android">

    <CheckBoxPreference
        android:title="change word"
        android:defaultValue="false"
        android:summaryOn="Show"
        android:summaryOff="Hidden"
        android:key="word"/>

    <EditTextPreference
        android:title="size"
        android:defaultValue="15"
        android:inputType="numberDecimal"
        android:key="size"/>

    <ListPreference
        android:title="color"
        android:defaultValue="black"
        android:entries="@array/color_show"
        android:entryValues="@array/color_show"
        android:key="color"/>
</PreferenceScreen>

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

    <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=".SettingsActivity"
            android:parentActivityName=".MainActivity">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".MainActivity"/>
        </activity>
    </application>

</manifest>

MainActivity.java

package com.example.admin.sharedpreferences;

import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.preference.PreferenceManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu,menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id=item.getItemId();
        switch (id){
            case R.id.menu_settings:
                Intent intent=new Intent(this,SettingsActivity.class);
                startActivity(intent);
                break;
        }
        return  true;
    }


    @Override
    protected void onStart() {
        super.onStart();

        SharedPreferences sharedPreferences=PreferenceManager.getDefaultSharedPreferences(this);
        TextView textView=findViewById(R.id.textview);
        if (sharedPreferences.getBoolean("word",false)){
            textView.setText("bye!");
        }
        String text=sharedPreferences.getString("color","black");
        if (text.equals("black")){
            textView.setTextColor(Color.BLACK);
        }else if (text.equals("red")){
            textView.setTextColor(Color.RED);
        }else if (text.equals("blue")){
            textView.setTextColor(Color.BLUE);
        }else  if (text.equals("green")){
            textView.setTextColor(Color.GREEN);
        }

        String sizeText=sharedPreferences.getString("size","15");
        int size=Integer.parseInt(sizeText);
        textView.setTextSize(size);
    }

SettingsActivity.java

package com.example.admin.sharedpreferences;

import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.ListPreference;
import android.preference.Preference;
import android.preference.PreferenceFragment;
import android.preference.PreferenceManager;
import android.support.v4.app.NavUtils;
import android.support.v7.app.AppCompatActivity;


public class SettingsActivity extends AppCompatActivity {
    @Override
    public void onCreate( Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_settings);
    }


    @Override
    public void onBackPressed() {
        super.onBackPressed();
        NavUtils.navigateUpFromSameTask(this);
    }

    public static class  preferenceFragment extends PreferenceFragment implements Preference.OnPreferenceChangeListener {

        @Override
        public void onCreate( Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            addPreferencesFromResource(R.xml.preferences_settings);
            Preference preference_size = findPreference("size");
            preferenceSummary(preference_size);
            Preference preference_color = findPreference("color");
            preferenceSummary(preference_color);
        }

        @Override
        public boolean onPreferenceChange(Preference preference, Object newValue) {
            String value=String.valueOf(newValue);
            if (preference instanceof ListPreference){
                ListPreference listPreference=(ListPreference) preference;
                int index=listPreference.findIndexOfValue(value);
                if (index >=0){
                    CharSequence[] text=listPreference.getEntries();
                    preference.setSummary(text[index]);
                }
            }else {
                preference.setSummary(value);
            }
            return true;
        }

        public void preferenceSummary(Preference preference) {
            preference.setOnPreferenceChangeListener(this );
            SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(preference.getContext());
            String text = sharedPreferences.getString(preference.getKey(), "");
            onPreferenceChange(preference, text);
        }
    }

}