Android進階___應用保活

基本概念

進程的優先級

安卓系統定義了了5個進程等級，當內存不不
⾜足的情況下按照5個優先級的不不同來決定到底先殺哪個進程。

如圖所示,優先級從大到小爲
1.前臺進程:
    Activity.onResume()
    與Service綁定的Activity
    被主動設置爲前臺模式的Service.startForeground()
    正在執行生命週期的回調的組件（onCreate()/onStart()/onDestroy()）
    正在執行BroadcastReceiver.onReceive();
2.可見進程
    Activity.onPause()
3.服務進程
    通過startService啓動的服務
4.後臺進程
    Activity.stop()
5.空進程
    不包含任何活動的組件.onStop       

如何提升進程的優先級

爲了實現提高app的存活率,我們的核心思路就是極可能的提高app進程的優先級.
例如qq掛一個像素點在前臺,讓其成爲前臺進程

實現像QQ一樣掛一個像素點在屏幕上

實現只有一個像素點的頁面

public class EmptyActivity extends Activity {
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //不設置佈局
//        setContentView(R.layout.activity_main);

        //在桌面繪製一個像素的內容
        Window window = getWindow();
        window.setGravity(Gravity.RIGHT|Gravity.BOTTOM);
        WindowManager.LayoutParams params = window.getAttributes();
        params.height=100;
        params.width=100;
        window.setAttributes(params);
    }
}

    <style name="KeepAlive">
        <!--設置窗口的背景爲透明-->
        <item name="android:windowBackground">@android:color/transparent</item>
        <!--設置窗口布局爲null-->
        <!--<item name="android:windowFrame">@null</item>-->
        <!--設置爲無標題欄-->
        <item name="android:windowNoTitle">true</item>
        <!--設置窗口樣式爲懸浮窗-->
        <item name="android:windowIsFloating">true</item>
        <!--設置背景爲不模糊-->
        <item name="android:backgroundDimEnabled">false</item>
        <!--不疊加-->
        <item name="android:windowContentOverlay">@null</item>
        <!--設置窗口爲半透明-->
        <item name="android:windowIsTranslucent">true</item>
        <!--設置act切換動畫爲null-->
        <item name="android:windowAnimationStyle">@null</item>
        <!--禁用啓動窗口-->
        <item name="android:windowDisablePreview">true</item>
        <!--設置展示Activity-->
        <item name="android:windowNoDisplay">false</item>
    </style>

在配置文件中應用
        <activity android:name=".EmptyActivity"
        android:theme="@style/KeepAlive">

創建一個空頁面的管理器,實現在服務中打開應用

public class ActManager {
    private static ActManager mInstance;
    private WeakReference<Activity> mReference;

    private ActManager() {
    }
    public static ActManager getInstance(){
        if (mInstance==null){
            synchronized (ActManager.class){
                if (mInstance==null){
                    mInstance=new ActManager();
                }
            }
        }
        return mInstance;
    }

    public void setAct(Activity act){
        mReference=new WeakReference<Activity>(act);
    }

    public void startAct(Context context){
        Intent intent = new Intent(context.getApplicationContext(),EmptyActivity.class);
        //application不能啓動act,因爲未設置啓動模式,所以我們給他加一個
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(intent);
    }
    public void finishAct(){
        if (mReference!=null&&mReference.get()!=null){
            mReference.get().finish();
        }
    }
}

封裝一個鎖屏和解鎖的廣播接收者

public class ScreenLIstener {
    private Callback mCallback;
    private Context mContext;
    ScreenListenerBrocastReceiver mScreenReceiver;

    public ScreenLIstener(Context context,Callback callback) {
        mContext=context;
        mCallback = callback;
        mScreenReceiver=new ScreenListenerBrocastReceiver();
        register();
    }

    private class ScreenListenerBrocastReceiver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            switch (action){
                case Intent.ACTION_SCREEN_ON:
                    if (mCallback!=null){
                        mCallback.onScreenOn();
                    }
                    break;
                case Intent.ACTION_SCREEN_OFF:
                    if (mCallback!=null){
                        mCallback.onScreenOff();
                    }
                    break;
            }
        }
    }



    private void register() {
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_SCREEN_ON);
        filter.addAction(Intent.ACTION_SCREEN_OFF);
        filter.addAction(Intent.ACTION_USER_PRESENT);
        mContext.registerReceiver(mScreenReceiver, filter);
    }
    public void unregister(){
        mContext.unregisterReceiver(mScreenReceiver);
    }

    public interface Callback{
        void onScreenOn();
        void onScreenOff();
    }
}

開啓一個服務

public class KeepAliveService extends Service {
    ScreenLIstener screenLIstener;

    @Override
    public void onCreate() {
        super.onCreate();
        //在熄屏時,打開頁面,在亮屏時結束頁面
        screenLIstener=new ScreenLIstener(this, new ScreenLIstener.Callback() {
            @Override
            public void onScreenOn() {
                Log.d("meee",getClass()+":\n"+"開屏幕:");
                ActManager.getInstance()
                        .finishAct();
                Toast.makeText(getApplicationContext(),"已解鎖",Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onScreenOff() {
                Log.d("meee",getClass()+":\n"+"鎖屏:");
                ActManager.getInstance()
                        .startAct(KeepAliveService.this);

            }
        });
    }

    @Override
    public IBinder onBind(Intent intent) {
        throw new UnsupportedOperationException("Not yet implemented");
    }
}