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;


   
    @Override
    protected 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.MyChronometer
        android: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 {




    @Override
    protected 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{

        @Override
        public void onLocationChanged(@NonNull Location location) {
            Log.d("ning","Location Changed "+location.toString());
        }

        @Override
        public void onLocationChanged(@NonNull List<Location> locations) {
            LocationListener.super.onLocationChanged(locations);
        }

        @Override
        public void onFlushComplete(int requestCode) {
            LocationListener.super.onFlushComplete(requestCode);
        }

        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {
            LocationListener.super.onStatusChanged(provider, status, extras);
        }

        @Override
        public void onProviderEnabled(@NonNull String provider) {
            LocationListener.super.onProviderEnabled(provider);
        }

        @Override
        public 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 {
    @Override
    public 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");
    }
}