JetPack入门

先导入依赖

   implementation("androidx.lifecycle:lifecycle-extensions:2.2.0")

1.使用LifeCycle解耦页面与组件

Activity

package com.tiger.lifecycle;import android.annotation.SuppressLint;
import android.os.Bundle;
import android.os.SystemClock;
import android.widget.Chronometer;import androidx.appcompat.app.AppCompatActivity;public class Step2Activity extends AppCompatActivity {private MyChronometer chronometer;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);chronometer = findViewById(R.id.chronometer);getLifecycle().addObserver(chronometer);//给自定义组件添加 Activity生命周期的这个一个监听}}

自定义组件

package com.tiger.lifecycle;import android.content.Context;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.widget.Chronometer;import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.LifecycleObserver;
import androidx.lifecycle.OnLifecycleEvent;public class MyChronometer extends Chronometer implements LifecycleObserver {private long elapsedTime=0;public MyChronometer(Context context, AttributeSet attrs) {super(context, attrs);}@OnLifecycleEvent(Lifecycle.Event.ON_RESUME) //在 resume 生命周期执行private void startMeter(){setBase(SystemClock.elapsedRealtime()-elapsedTime);start();}@OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)//在 PAUSE 生命周期执行private void stopMeter(){elapsedTime = SystemClock.elapsedRealtime() - getBase();stop();}}

xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".Step1Activity"><com.tiger.lifecycle.MyChronometerandroid:id="@+id/chronometer"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Hello World!"android:textSize="30sp"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintRight_toRightOf="parent"app:layout_constraintTop_toTopOf="parent"></com.tiger.lifecycle.MyChronometer></androidx.constraintlayout.widget.ConstraintLayout>

2.使用LifeCycle解耦Service与组件

activity

package com.tiger.lifecycle;import android.content.Intent;
import android.os.Bundle;
import android.view.View;import androidx.appcompat.app.AppCompatActivity;public class Step3Activity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main_two);}public void startGps(View view) {startService(new Intent(this,MyLocationService.class));}public void stopGps(View view) {stopService(new Intent(this,MyLocationService.class));}
}

service

package com.tiger.lifecycle;import android.util.Log;import androidx.lifecycle.LifecycleService;public class MyLocationService extends LifecycleService {public MyLocationService() {Log.d("ning","MyLocationService init");MyLocationObserver myLocationObserver = new MyLocationObserver(this);getLifecycle().addObserver(myLocationObserver);}}

observer

package com.tiger.lifecycle;import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.util.Log;import androidx.annotation.NonNull;
import androidx.core.app.ActivityCompat;
import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.LifecycleObserver;
import androidx.lifecycle.OnLifecycleEvent;import java.util.List;public class MyLocationObserver implements LifecycleObserver {private Context context;private LocationManager locationManager;private MyLocationListener myLocationListener;public MyLocationObserver(Context context) {this.context = context;}@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)private void startGetLocation() {Log.d("ning","startGetLocation");locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);myLocationListener = new MyLocationListener();if (ActivityCompat.checkSelfPermission(context, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(context, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {//不满足就退出方法return;}locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 3000, 1, myLocationListener);//提供监听 GPS提供 ，每3秒获取一下信息，每拿手机移动一米获取一下信息}@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)private void stopGetLocation(){Log.d("ning","stopGetLocation");locationManager.removeUpdates(myLocationListener);}static class MyLocationListener implements LocationListener{@Overridepublic void onLocationChanged(@NonNull Location location) {Log.d("ning","Location Changed "+location.toString());}@Overridepublic void onLocationChanged(@NonNull List<Location> locations) {LocationListener.super.onLocationChanged(locations);}@Overridepublic void onFlushComplete(int requestCode) {LocationListener.super.onFlushComplete(requestCode);}@Overridepublic void onStatusChanged(String provider, int status, Bundle extras) {LocationListener.super.onStatusChanged(provider, status, extras);}@Overridepublic void onProviderEnabled(@NonNull String provider) {LocationListener.super.onProviderEnabled(provider);}@Overridepublic void onProviderDisabled(@NonNull String provider) {LocationListener.super.onProviderDisabled(provider);}}}

3.使用ProcessLifecycleOwner监听应用程序生命周期

package com.tiger.lifecycle;import android.util.Log;import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.LifecycleObserver;
import androidx.lifecycle.OnLifecycleEvent;public class ApplicationObserver implements LifecycleObserver {private String TAG = "ning";@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)public void onCreate() {Log.d(TAG, "Lifecycle.Event.ON_CREATE");}@OnLifecycleEvent(Lifecycle.Event.ON_START)public void onStart() {Log.d(TAG, "Lifecycle.Event.ON_START");}@OnLifecycleEvent(Lifecycle.Event.ON_RESUME)public void onResume() {Log.d(TAG, "Lifecycle.Event.ON_RESUME");}@OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)public void onPause() {Log.d(TAG, "Lifecycle.Event.ON_PAUSE");}@OnLifecycleEvent(Lifecycle.Event.ON_STOP)public void onStop() {Log.d(TAG, "Lifecycle.Event.ON_STOP");}@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)public void onDestroy() {Log.d(TAG, "Lifecycle.Event.ON_DESTROY");}}

MyApplication

package com.tiger.lifecycle;import android.app.Application;
import android.util.Log;import androidx.lifecycle.ProcessLifecycleOwner;public class MyApplication extends Application {@Overridepublic void onCreate() {super.onCreate();ProcessLifecycleOwner.get().getLifecycle().addObserver(new ApplicationObserver());//只有一个会执行，多个Activity只执行一次Log.d("ning","MyApplication onCreate");}
}