数据存储——四种存储方式——Application的生命周期

深藏阁楼爱情的钟 2023-09-28 14:34 131阅读 0赞

Application是Android的一大组件，在App运行过程中有且仅有一个Application对象贯穿整个生命周期。

在AndroidManifest.xml里面，activity节点的上级正是application节点。如果给application节点指定android:name属性，则表示App将运行自定义名称的Application代码。

需要注意，Application的onCreate方法调用先于Activity的onCreate方法调用。但是，Application的onTerminate方法纯属摆设，永远不会被调用。

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<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.myapplication">
    
        
        <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
        <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
        
        <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
    
        <application
            android:name=".MainApplication"
            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/Theme.MyApplication">
            <activity
                android:name=".MainActivity2"
                android:exported="false" />
            <activity
                android:name=".MainActivity"
                android:exported="true">
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
    
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
        </application>
    
    </manifest>

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package com.example.myapplication;
    
    import android.app.Application;
    import android.util.Log;
    
    public class MainApplication extends Application
    {
        private final static String TAG = "MainApplication";
    
        @Override
        public void onCreate()
        {
            super.onCreate();
            Log.d(TAG, "onCreate");
    
        }
    
        @Override
        public void onTerminate() {
            super.onTerminate();
            Log.d(TAG, "onTerminate");
        }
    
    }

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![cc7b1050240da593877073d9fe4ff713.png][]

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[cc7b1050240da593877073d9fe4ff713.png]: https://img-blog.csdnimg.cn/img_convert/cc7b1050240da593877073d9fe4ff713.png
[9cc8b327e8cf0de4c8d7500a470957a3.png]: https://img-blog.csdnimg.cn/img_convert/9cc8b327e8cf0de4c8d7500a470957a3.png
[edf16d51c09050af88dd171f2f3aeb23.png]: https://img-blog.csdnimg.cn/img_convert/edf16d51c09050af88dd171f2f3aeb23.png
[91ab4374f66016b39ab843357f1da0dd.png]: https://img-blog.csdnimg.cn/img_convert/91ab4374f66016b39ab843357f1da0dd.png