Service
不是一个独立的进程，也不是线程
两种：start 和 Bind
在AndroidManifest.xml中声明：
<service android:name=".MusicService" />
service with start ：
package com.jsc4.aboutactivity;
import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;
import android.util.Log;
import androidx.annotation.Nullable;
public class MusicService extends Service {
private static final String TAG = MusicService.class.getSimpleName();
private MediaPlayer mMediaPlayer;
@Override
public void onCreate() {
super.onCreate();
Log.i(TAG, "onCreate");
mMediaPlayer = MediaPlayer.create(this, R.raw.lovelove);
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i(TAG, "onStartCommand");
mMediaPlayer.start();
return super.onStartCommand(intent, flags, startId);
}
@Override
public void onDestroy() {
Log.i(TAG, "onDestroy");
mMediaPlayer.stop();
super.onDestroy();
}
@Nullable
@Override
public IBinder onBind(Intent intent) {
Log.i(TAG, "onBind");
return null;
}
}
Service声明周期
service with bind：
MusicButtonActivity.java
package com.jsc4.aboutactivity;
import androidx.appcompat.app.AppCompatActivity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.view.View;
import android.widget.Button;
public class MusicButtonActivity extends AppCompatActivity implements View.OnClickListener {
private Button mStartButton;
private Button mStopButton;
private MusicService mMusicService;
private ServiceConnection mServiceConnection = new ServiceConnection(){
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
MusicService.LocalBinder localBinder = (MusicService.LocalBinder) service;
mMusicService = localBinder.getService();
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_music_button);
mStartButton = findViewById(R.id.start_music_button);
mStopButton = findViewById(R.id.stop_music_button);
mStartButton.setOnClickListener(this);
mStopButton.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch(v.getId()){
case R.id.start_music_button:
startService(new Intent(MusicButtonActivity.this, MusicService.class));
bindService(new Intent(MusicButtonActivity.this, MusicService.class), mServiceConnection, BIND_AUTO_CREATE);
break;
case R.id.stop_music_button:
unbindService(mServiceConnection);
stopService(new Intent(MusicButtonActivity.this, MusicService.class));
break;
case R.id.get_music_progress_button:
if(mMusicService != null){
int progress = mMusicService.getMusicPlayProgress();
}
break;
}
}
}
MusicService.java
package com.jsc4.aboutactivity;
import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;
import androidx.annotation.Nullable;
public class MusicService extends Service {
private static final String TAG = MusicService.class.getSimpleName();
private MediaPlayer mMediaPlayer;
private IBinder mIBinder = new LocalBinder();
@Override
public void onCreate() {
super.onCreate();
Log.i(TAG, "onCreate");
mMediaPlayer = MediaPlayer.create(this, R.raw.lovelove);
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i(TAG, "onStartCommand");
mMediaPlayer.start();
return super.onStartCommand(intent, flags, startId);
}
@Override
public void onDestroy() {
Log.i(TAG, "onDestroy");
mMediaPlayer.stop();
super.onDestroy();
}
@Nullable
@Override
public IBinder onBind(Intent intent) {
Log.i(TAG, "onBind");
return mIBinder;
}
public class LocalBinder extends Binder {
MusicService getService(){
return MusicService.this;
}
}
public int getMusicPlayProgress(){
return 18;
}
}
工作流程：
Activity中的这句话（bindService(new Intent(MusicButtonActivity.this, MusicService.class), mServiceConnection, BIND_AUTO_CREATE);）会把connection传给service，service中的这句话（return mIBinder;）会把mIBinder传回去，传给刚才传进来的connection里，在Activity中就可以收到了：
private ServiceConnection mServiceConnection = new ServiceConnection(){
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
MusicService.LocalBinder localBinder = (MusicService.LocalBinder) service;
mMusicService = localBinder.getService();
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
Activity收到的IBinder对象含有关键信息，因为在service中这个IBinder对象中定义了getService方法，这样就可以在Activity中拿到Service了。
在service中定义了一些公共方法，如public int getMusicPlayProgress();，这样，在Activity中，通过service对象，就可以获取到这些公共方法了。
IntentService
activity中：
Intent intent = new Intent(MusicButtonActivity.this, MusicService.class);
intent.putExtra("msg", "携带的信息");
startService(intent);
IntentService中:
@Override
protected void onHandleIntent(@Nullable Intent intent) {
// intent队列 排队，像MessageQueue 同步操作：排队领书，处理Intent数据
// stopSelf(); // 停止本身，此处不必使用
if(intent != null){
}
}
整个IntentService：
package com.jsc4.aboutactivity;
import android.app.IntentService;
import android.content.Intent;
import androidx.annotation.Nullable;
public class TestIntentService extends IntentService {
/**
* Creates an IntentService. Invoked by your subclass's constructor.
*
* @param name Used to name the worker thread, important only for debugging.
*/
public TestIntentService(String name) {
super(name);
}
@Override
public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
// do more work is wrong UI线程 > 10s时，ANR（应用程序无响应）
// 把耗时操作放到子线程中
Thread thread = new Thread(new Runnable() {
@Override
public void run() {
}
});
thread.start();
return super.onStartCommand(intent, flags, startId);
}
@Override
protected void onHandleIntent(@Nullable Intent intent) {
// intent队列 排队，像MessageQueue 同步操作：排队领书，处理Intent数据
// stopSelf(); // 停止本身，此处不必使用
if(intent != null){
}
}
}
注意
Service中不适合做耗时操作，它属于UI线程，所以要创建一个子线程去做耗时操作。
扫描二维码关注公众号，回复：
12076347 查看本文章
