Android四大组件

code-Android
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Android四大组件

Gerneral

Android开发常用知识储备。Android的四大组件中除了BroadCastReceiver以外，其他三种组件都必须在AndroidManifest中注册
才能使用

Activity

activity

  1. Activity生命周期
  • 完整生存期：活动在onCreate()和onDestroy()方法之间所经历的
  • 可见生存期：活动在onStart()和onStop()方法之间所经历的
  • 交互活动期：活动在onResume()和onPause()方法之间所经历的
  1. Activity注册
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    <activity android:name="com.lang.payhelper.SettingActivity"/>
  2. 容易忽略重点
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    @Override
    public void onBackPressed() {
        // sendmsg("触发 onBackPressed"); 界面上的回退
        moveTaskToBack(true);
    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        // 过滤按键动作
        if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
            sendmsg("触发 KeyEvent.KEYCODE_BACK");
            moveTaskToBack(true);
        }
        return super.onKeyDown(keyCode, event);
    }
    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        // 异常恢复 
        // TODO:这个还不是很理解
        super.onRestoreInstanceState(savedInstanceState);
    }

Service

Service

  1. 注册service
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    <service
        android:name="com.lang.payhelper.payhook.DaemonService"
        android:enabled="true"
        android:exported="false"
        android:process=":daemon_service" />
  2. 启动service方式
  • 本进程 startService(new Intent(this, DaemonService.class));
  • 非本进程 bindService （案例 https://blog.csdn.net/iispring/article/details/48169339 ）
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    bindService(intent, new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
        }
        @Override
        public void onServiceDisconnected(ComponentName componentName) {
        }
    },BIND_AUTO_CREATE);

BroadcastReceiver

  1. 动态注册 registerReceiver(Received, intentFilter);
  • Received 处理广播的类，继承BroadcastReceiver
  • intentFilter 关注的话题
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    IntentFilter intentFilter = new IntentFilter();
    intentFilter.addAction(BILLRECEIVED_ACTION);
  1. 静态注册
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    <receiver android:name=".activity.broadcastreceiver.staticregist.StaticReceiver">
        <intent-filter>
            <action android:name="com.broadcast.static"/>
        </intent-filter>
    </receiver>
  2. 有序广播 priority越小优先执行
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    <receiver
        android:name=".activity.broadcastreceiver.orderregist.FirstReceiver">
        <intent-filter android:priority="300">
            <action android:name="com.broadcast.order"/>
        </intent-filter>
    </receiver>
    <receiver
        android:name=".activity.broadcastreceiver.orderregist.SecondReceiver">
        <intent-filter android:priority="200">
            <action android:name="com.broadcast.order"/>
        </intent-filter>
    </receiver>
    <receiver
        android:name=".activity.broadcastreceiver.orderregist.ThirdReveiver">
        <intent-filter android:priority="100">
            <action android:name="com.broadcast.order"/>
        </intent-filter>
    </receiver>
  3. 本地广播

ContentProvider

  1. 原理
    数据通过唯一的 URI 标识来源。ContentProvider 将数据看作表，查询 / 操作数据的时候，通过类似数据库操作的 insert / delete / query / update 方法来实现增删查改操作。因此包含数据提供方和使用方
  2. 提供方 Provider (案例 https://www.jianshu.com/p/ac40ed95d577)
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    <permission
        android:name="com.straw.providerhost.course.read"
        android:protectionLevel="normal"/>
    <permission
        android:name="com.straw.providerhost.course.write"
        android:protectionLevel="normal"/>

    <application>
        <provider
            android:authorities="com.straw.course"
            android:name="com.straw.providerhost.CourseContentProvider"
            android:exported="true"
            android:readPermission="com.straw.providerhost.course.read"
            android:writePermission="com.straw.providerhost.course.write"/>
    </application>
  3. 使用方 ContentReciver.query(uri)的方式获取数据