Android进阶___应用保活

基本概念

进程的优先级

安卓系统定义了了5个进程等级，当内存不不
⾜足的情况下按照5个优先级的不不同来决定到底先杀哪个进程。

如图所示,优先级从大到小为
1.前台进程:
    Activity.onResume()
    与Service绑定的Activity
    被主动设置为前台模式的Service.startForeground()
    正在执行生命周期的回调的组件（onCreate()/onStart()/onDestroy()）
    正在执行BroadcastReceiver.onReceive();
2.可见进程
    Activity.onPause()
3.服务进程
    通过startService启动的服务
4.后台进程
    Activity.stop()
5.空进程
    不包含任何活动的组件.onStop       

如何提升进程的优先级

为了实现提高app的存活率,我们的核心思路就是极可能的提高app进程的优先级.
例如qq挂一个像素点在前台,让其成为前台进程

实现像QQ一样挂一个像素点在屏幕上

实现只有一个像素点的页面

public class EmptyActivity extends Activity {
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //不设置布局
//        setContentView(R.layout.activity_main);

        //在桌面绘制一个像素的内容
        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">
        <!--设置窗口的背景为透明-->
        <item name="android:windowBackground">@android:color/transparent</item>
        <!--设置窗口布局为null-->
        <!--<item name="android:windowFrame">@null</item>-->
        <!--设置为无标题栏-->
        <item name="android:windowNoTitle">true</item>
        <!--设置窗口样式为悬浮窗-->
        <item name="android:windowIsFloating">true</item>
        <!--设置背景为不模糊-->
        <item name="android:backgroundDimEnabled">false</item>
        <!--不叠加-->
        <item name="android:windowContentOverlay">@null</item>
        <!--设置窗口为半透明-->
        <item name="android:windowIsTranslucent">true</item>
        <!--设置act切换动画为null-->
        <item name="android:windowAnimationStyle">@null</item>
        <!--禁用启动窗口-->
        <item name="android:windowDisablePreview">true</item>
        <!--设置展示Activity-->
        <item name="android:windowNoDisplay">false</item>
    </style>

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

创建一个空页面的管理器,实现在服务中打开应用

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不能启动act,因为未设置启动模式,所以我们给他加一个
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(intent);
    }
    public void finishAct(){
        if (mReference!=null&&mReference.get()!=null){
            mReference.get().finish();
        }
    }
}

封装一个锁屏和解锁的广播接收者

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();
    }
}

开启一个服务

public class KeepAliveService extends Service {
    ScreenLIstener screenLIstener;

    @Override
    public void onCreate() {
        super.onCreate();
        //在熄屏时,打开页面,在亮屏时结束页面
        screenLIstener=new ScreenLIstener(this, new ScreenLIstener.Callback() {
            @Override
            public void onScreenOn() {
                Log.d("meee",getClass()+":\n"+"开屏幕:");
                ActManager.getInstance()
                        .finishAct();
                Toast.makeText(getApplicationContext(),"已解锁",Toast.LENGTH_SHORT).show();
            }

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

            }
        });
    }

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