Service能否执行耗时操作
Service和Activity一样都是运行在主线程的，配置下android的Process属性可以让service在另外的进程中执行
service生命周期
service有三种启动模式，绑定模式，非绑定模式和混合模式
非绑定模式：
- startService()：onCreate(); onStartCommand();
- stopService()：onDestory();
绑定模式：
- bindService(): onCreate(); onBind();
- unbindService(): onUnbind(); onDestroy();
IntentService介绍
- 首先是Service的子类，但它会创建独立的worker线程在onHandleIntent()方法中处理耗时操作
- 请求处理完成后，IntentService会自动停止，无需调用stopSelf()方法停止Service;
- 为 Service 的 onBind()提供默认实现，返回 null
- 为 Service 的 onStartCommand 提供默认实现，将请求 Intent 添加到队列中
MainActivity.java
public void click(View view) {
Intent intent = new Intent(this, MyIntentService.class);
intent.putExtra("start", "MyIntentService");
startService(intent);
}
MyIntentService.java
public class MyIntentService extends IntentService {
private String ex = "";
private Handler mHandler = new Handler(){
public void handleMessage(android.os.Message msg) {
Toast.makeText(getApplicationContext(), "-e: "+ex, Toast.LENGTH_LONG).show();
};
};
// 注意：这里必须要有无参构造函数
// RuntimeException: MyIntentService has no zero argment constructor
public MyIntentService() {
super("MyIntentService");
}
// 为 Service 的 onStartCommand 提供默认实现，将请求 Intent 添加到队列中
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
ex = intent.getStringExtra("start");
return super.onStartCommand(intent, flags, startId);
}
// 为 Service 的 onBind()提供默认实现，返回 null
@Override
public IBinder onBind(Intent intent) {
return super.onBind(intent);
}
// 会创建独立的 worker 线程来处理 onHandleIntent()方法实现的代码，处理耗时操作
// 请求处理完成后，IntentService 会自动停止，无需调用 stopSelf()方法停止 Service;
@Override
protected void onHandleIntent(Intent intent) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
mHandler.sendEmptyMessage(0);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
Activity,Intent,Service是什么关系
Activity和Service是Context的子类，是ContextWrapper的子类。它们之间可以通过Intent传递数据。
Service的onStartCommand()有几种返回值?代表什么?
有四种返回值。
START_STICKY: 服务被杀死会重启，但是Intent对象没有保存
START_NOT_STICKY：执行完onStartCommand()后，服务被杀死不会重启
START_REDELIVER_INTENT：服务被杀死会重启，并传入Intent
START_STICKY_COMPATIBILITY：START_STICKY的兼容版本，但服务被杀死不一定能重启
Service的onRebind(Intent)在什么情况下会执行?
在onUnbind()方法返回true的时候会执行，否则不执行
Activity调用Service的方法有哪些方式
一：bindService绑定服务，传入ServiceConnection接口的实现类，在该接口的onServiceConnected()回调中获取Binder子类
Intent intent = new Intent(this, BaoService.class);
MyConnection conn = new MyConnection();
bindService(intent, conn, BIND_AUTO_CREATE);
class MyConnection implements ServiceConnection{
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
zms = (PublicBusiness) service;
}
@Override
public void onServiceDisconnected(ComponentName name) {
// TODO Auto-generated method stub
}
}
zms.qianXian();
//----------------------------------------
public class BaoService extends Service {
@Override
public IBinder onBind(Intent intent) {
System.out.println("bind");
return new ZhongMiShu();
}
class ZhongMiShu extends Binder implements PublicBusiness{
@Override
public void qianXian(){
BaoService.this.banZheng();
}
}
public void banZheng() {
System.out.println("钱一收到，证就办好");
}
}
//--------------------------------------
public interface PublicBusiness {
void qianXian();
}
二：Messenger方式：onBind()方法返回Messenger对象
public class MainActivity extends AppCompatActivity {
Messenger mService = null;
boolean mBound;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
protected void onStart() {
super.onStart();
bindService(new Intent(this, MessengerService.class), mConnection, Context.BIND_AUTO_CREATE);
}
@Override
protected void onStop() {
super.onStop();
if (mBound){
unbindService(mConnection);
mBound = false;
}
}
private ServiceConnection mConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
mService = new Messenger(service);
mBound = true;
}
@Override
public void onServiceDisconnected(ComponentName name) {
mService = null;
mBound = false;
}
};
public void sayHello(View view){
if (!mBound) return;
Message msg = Message.obtain(null, MessengerService.MSG_SAY_HELLO, 0, 0);
try {
mService.send(msg);
}catch (RemoteException e){
e.printStackTrace();
}
}
}
public class MessengerService extends Service {
static final int MSG_SAY_HELLO = 1;
class IncomingHandler extends Handler{
@Override
public void handleMessage(Message msg) {
switch (msg.what){
case MSG_SAY_HELLO:
Toast.makeText(getApplicationContext(),"hello",Toast.LENGTH_SHORT).show();
break;
default:
super.handleMessage(msg);
}
}
}
final Messenger mMessenger = new Messenger(new IncomingHandler());
@Nullable
@Override
public IBinder onBind(Intent intent) {
Toast.makeText(getApplicationContext(),"binding",Toast.LENGTH_SHORT).show();
return mMessenger.getBinder();
}
}
三：AIDL 进程间通讯
aidl 是Android interface definition Language 的英文缩写，意思Android 接口定义语言。aidl 可以帮助我们发布以及调用远程服务，实现跨进程通信。
- 将对应的aidl后缀文件放到src目录下会自动生成对应的接口类
- 将对应的aidl文件拷贝到相同路径的包下
- 通过bindService(Intent, ServiceConnection, int); 实现ServiceConnection接口的onServiceConnected方法获取代理对象IBinder
- 通过
Stub.asInterface(IBinder);获取得到aidl生成的接口类，即可调用跨进程方法