Android实现简单的检测手机自由落体关闭屏幕
实现功能如下:在背景运行app,检测到自由落体状态时,熄灭屏幕,可重复测试。
1. 检测自由落体动作
需要使用到加速度感应器 TYPE_ACCELEROMETER
SensorManager mSensorManager; private float mLastX; private float mLastY; private float mLastZ; private double force; @Override public void onCreate() { super.onCreate(); mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE); mSensorManager.registerListener(sensorListener, mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_GAME); } private final SensorEventListener sensorListener = new SensorEventListener() { @Override public void onSensorChanged(SensorEvent event) { try { if(event.sensor == null){ return; } }catch (Exception ex){ } if(event.sensor.getType() == Sensor.TYPE_ACCELEROMETER){ mLastX = event.values[0]; mLastY = event.values[1]; mLastZ = event.values[2]; force = Math.sqrt(mLastX*mLastX+mLastY*mLastY+mLastZ*mLastZ); } if(force < 1 ){ Log.i("Kunkka","force < 1 START-------------"); new Handler().postDelayed(new Runnable() { @Override public void run() { if (force < 1) { Log.i("Kunkka","force < 1 END, SCREEN OFF"); screenOff(); } } }, 20); } } @Override public void onAccuracyChanged(Sensor sensor, int accuracy) { } };
标黄的是判断手机失重的依据,即三个方向的合力为0。由于不是那么精确,让其合力<1即可。
另外为了防止手机平时突然出现符合这个结果的,当第一次出现符合条件的合力时,延迟20ms再检测一次,(最好连续检测多次来确定连续处于失重状态),假如依旧符合失重,就认定此时在失重状态。再做下一步的处理。
2. 关闭屏幕
熄灭屏幕代码:
private void screenOff(){ DevicePolicyManager policyManager = (DevicePolicyManager) getSystemService(Context.DEVICE_POLICY_SERVICE); ComponentName adminReceiver = new ComponentName(DeviceFallDetectService.this, MyAdminReceiver.class); boolean admin = policyManager.isAdminActive(adminReceiver); if (admin) { policyManager.lockNow(); } else { Toast.makeText(this,"没有设备管理权限", Toast.LENGTH_LONG).show(); } }
息屏主要使用的是DevicePolicyManager 类,此外MyAdminReceiver是一个息屏管理的广播接收器,该接受器非常重要,系统设置中正是通过该接收器才找到的应用程序,该广播接收器在AndroidManifest.xml中的声明如下:
<receiver android:name=".MyAdminReceiver" android:permission="android.permission.BIND_DEVICE_ADMIN"> <meta-data android:name="android.app.device_admin" android:resource="@xml/admin"/> <intent-filter> <action android:name="android.app.action.DEVICE_ADMIN_ENABLED"/> </intent-filter> </receiver>
xml/admin.xml文件内容如下:
<?xml version="1.0" encoding="utf-8"?> <device-admin xmlns:android="http://schemas.android.com/apk/res/android" > <uses-policies> <force-lock /> </uses-policies> </device-admin>
Receiver的源码空的就可以,只需要继承DeviceAdminReceiver:
public class MyAdminReceiver extends DeviceAdminReceiver { }
网上说还需要加权限
<uses-permission android:name="android.permission.USES_POLICY_FORCE_LOCK" />
但我没加去运行也没出什么问题。
3. Forground service实现重复运行
由于运行在background service中的话,屏幕关了再打开,好像background service就被停下了。
为了每次屏幕亮了都可以继续运行,把service改成O之后的foreground service:
首先startservice的地方,改成foreground方式启动:
Intent intent = new Intent(MainActivity.this, DeviceFallDetectService.class); startForegroundService(intent); MainActivity.this.finish();
然后在service的onStartCommand中,立刻声明startForeground。
并且android O 以后每个Notification都需要依附一个channel,要不然就报错。加一个简单的channel:
@Override public int onStartCommand(Intent intent, int flags, int startId) { initChanel(); return super.onStartCommand(intent, flags, startId); } private void initChanel(){ NotificationChannel channel = new NotificationChannel(CHANNEL_ID,"FallDetect", NotificationManager.IMPORTANCE_HIGH); NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE); manager.createNotificationChannel(channel); Notification notification = new Notification.Builder(getApplicationContext(),CHANNEL_ID).build(); startForeground(3210, notification); }
大功告成