Android中bindService开发步骤

分类：Android, Java 阅读 (2,465)

5月 082016

转载请注明原文地址：http://bcoder.com/java/development-steps-of-bindservice-in-android

一、先简单首先回顾一下Service的一些问题

1、为什么使用Service？

答：对于一些需要长时间才可执行完毕的操作放在Activity里不太合适，因为Activity关闭后导致操作不能再继续，但后台服务可以持续运行。

2、bindService和startService的区别？

答：１）两者创建的service的生命周期不同

２）startService启动的服务不能返回service的实例，bindService的可以

3、为什么不直接使用new XxxxService来创建服务？

答：在执行startService或者bindService时，android会把会启动的服务进行记录（未做深入研究），以确保拥有后台服务的进程具有较高的优先级，所以要使用startService或者bindService来创建服务。new XxxxService只是创建了一个服务类的实例，而不是一个服务。

4、为什么onServiceDisconnected一直未被调用到？

答：unbindService并不会导致onServieDisconnected被调用，只有在服务被系统销毁的时候才会被调用。

5、可以在一个应用中使用startService跨进程启动另外一个进程的服务吗？

答：可以，需要设置目标进程的包名，可以使用如下代码或者setPackage(未测试)

        Intent intent = new Intent();
        intent.setClassName("com.zht.car.testservice", "com.zht.car.testservice.MyTestService");
        startService(intent);

Intent intent = new Intent();

intent.setClassName("com.zht.car.testservice", "com.zht.car.testservice.MyTestService");

startService(intent);

6、既然可以跨进程调用startService那为什么还要使用aidl？

答：startService只能启动另外进程的服务，最多还可以通过intent传入一些参数，但是不能从对方进程返回数据，所以如果跨进程通讯aidl还是很有必要的。

二、bindService的开发步骤简述

1、创建一个Service，比如本例中为MyTestService

2、在Service中定义一个Binder的子类MyServiceBinder，后面用来返回MyTestService的实例（见一、３为什么不能直接new MyTestService() ）

3、定义并实例化一个MyServiceBinder对象，用来在Service的onBind函数中返回给调用者

4、在Service的onBind函数中返回MyServiceBinder实例对象，android sdk会通过各种调用将这个对象传到ServiceConnection的onServiceConnected

5、在Activity中定义一个MyTestService对象

6、在Activity中执行bindService

7、在Activity中实例化一个ServiceConnection对象

8、在ServiceConnection对象的onServiceConnected回调函数中，将参数中的IBinder对象强制转换为Service中定义的Binder子类（MyServiceBinder）对象

9、通过强制Binder子类对象的方法获取MyTestService实例，至此就得到这个Service的实例了

10、绑定状态的控制，通过一个boolean类型的变量来控制，以及其他的回调函数的设置

三、时序图

四、代码

１、Service的代码

package com.zht.car.testservice;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.Handler;
import android.os.IBinder;

public class MyTestService extends Service {
    private MyServiceBinder mMyServiceBinder = new MyServiceBinder();

    private OnWeightChangeListener mOnWeightChangeListener;

    private int mWeight = 20;

    public MyTestService() {

    }

    @Override
    public IBinder onBind(Intent intent) {
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                mWeight = mWeight * 2;
                if(mOnWeightChangeListener != null){
                    mOnWeightChangeListener.onWeightChange(mWeight);
                }
            }
        }, 1000);
        return mMyServiceBinder;
    }

    class MyServiceBinder extends Binder {
        MyTestService getService(){
            return MyTestService.this;
        }
    }

    public int getWeight() {
        return mWeight;
    }

    public void setOnWeightChangeListener(OnWeightChangeListener onWeightChangeListener) {
        mOnWeightChangeListener = onWeightChangeListener;
    }

    public interface OnWeightChangeListener {
        public void onWeightChange(int weight);
    }
}

package com.zht.car.testservice;

import android.app.Service;

import android.content.Intent;

import android.os.Binder;

import android.os.Handler;

import android.os.IBinder;

public class MyTestService extends Service {

private MyServiceBinder mMyServiceBinder = new MyServiceBinder();

private OnWeightChangeListener mOnWeightChangeListener;

private int mWeight = 20;

public MyTestService() {

}

@Override

public IBinder onBind(Intent intent) {

new Handler().postDelayed(new Runnable() {

@Override

public void run() {

mWeight = mWeight * 2;

if(mOnWeightChangeListener != null){

mOnWeightChangeListener.onWeightChange(mWeight);

}

}, 1000);

return mMyServiceBinder;

}

class MyServiceBinder extends Binder {

MyTestService getService(){

return MyTestService.this;

}

public int getWeight() {

return mWeight;

}

public void setOnWeightChangeListener(OnWeightChangeListener onWeightChangeListener) {

mOnWeightChangeListener = onWeightChangeListener;

}

public interface OnWeightChangeListener {

public void onWeightChange(int weight);

}

２、Activity代码

package com.zht.car.testservice;

import android.app.Service;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class MainActivity extends AppCompatActivity {
    private MyTestService mMyTestService;
    private String LOG_TAG = "MainActivity";

    private boolean mServiceBinded = false;

    private ServiceConnection mServiceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            MyTestService.MyServiceBinder binder = (MyTestService.MyServiceBinder) service;
            mMyTestService = binder.getService();
            mMyTestService.setOnWeightChangeListener(new MyTestService.OnWeightChangeListener() {
                @Override
                public void onWeightChange(int weight) {
                    Log.d(LOG_TAG, "Weight changed: " + mMyTestService.getWeight());
                }
            });
            mServiceBinded = true;
            Log.d(LOG_TAG, "Service connected.");
            Log.d(LOG_TAG, "weight: " + mMyTestService.getWeight());
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            Log.d(LOG_TAG, "Service disconnected.");
            mServiceBinded = false;
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onDestroy() {
        if(mServiceBinded) {
            unbindService(mServiceConnection);
        }
        super.onDestroy();
    }

    public void onBindServiceClick(View view) {
        if(mServiceBinded){
            return;
        }

        Intent intent = new Intent(this, MyTestService.class);
        bindService(intent, mServiceConnection, Service.BIND_AUTO_CREATE);
    }

    public void onUnbindServiceClick(View view) {
        if(!mServiceBinded) {
            return;
        }

        unbindService(mServiceConnection);
        mServiceBinded = false;
    }
}

package com.zht.car.testservice;

import android.app.Service;

import android.content.ComponentName;

import android.content.Intent;

import android.content.ServiceConnection;

import android.os.IBinder;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

public class MainActivity extends AppCompatActivity {

private MyTestService mMyTestService;

private String LOG_TAG = "MainActivity";

private boolean mServiceBinded = false;

private ServiceConnection mServiceConnection = new ServiceConnection() {

@Override

public void onServiceConnected(ComponentName name, IBinder service) {

MyTestService.MyServiceBinder binder = (MyTestService.MyServiceBinder) service;

mMyTestService = binder.getService();

mMyTestService.setOnWeightChangeListener(new MyTestService.OnWeightChangeListener() {

@Override

public void onWeightChange(int weight) {

Log.d(LOG_TAG, "Weight changed: " + mMyTestService.getWeight());

}

});

mServiceBinded = true;

Log.d(LOG_TAG, "Service connected.");

Log.d(LOG_TAG, "weight: " + mMyTestService.getWeight());

}

@Override

public void onServiceDisconnected(ComponentName name) {

Log.d(LOG_TAG, "Service disconnected.");

mServiceBinded = false;

}

};

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

@Override

protected void onDestroy() {

if(mServiceBinded) {

unbindService(mServiceConnection);

}

super.onDestroy();

}

public void onBindServiceClick(View view) {

if(mServiceBinded){

return;

}

Intent intent = new Intent(this, MyTestService.class);

bindService(intent, mServiceConnection, Service.BIND_AUTO_CREATE);

}

public void onUnbindServiceClick(View view) {

if(!mServiceBinded) {

return;

}

unbindService(mServiceConnection);

mServiceBinded = false;

}

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