Android笔记（五十九）Android总结：四大组件——Service篇

什么是服务？

服务（service）是Android中实现程序后台运行的解决方案，适用于去执行那些不需要和用户交互并且还需要长期运行的任务。服务的运行不依赖于任何用户界面。

服务运行在主线程中，所以在service不能用来做一些耗时操作。

服务的用法

1.新建一个继承自Service的类，并实现其抽象方法

2.构建一个Intent

3.使用startService(intent)启动服务

4.使用stopService(intent)停止服务

服务在创建的时候会调用其onCreate()方法，而在每次启动服务的时候都会调用onStartCommand()方法，在服务销毁的时候会调用onDestroy()方法。

Service和Activity的通信

在现实编程中，我们除了要开启关闭Service之外，我们往往还需要获取Service执行的步骤、进度等等，这就需要Service和Activity之间进行通信。

想要Activity和Service之间进行通信，需要使用bindService()和unbindService()方法启动、关闭Service。

bindService()方法有三个参数，分别是：

1.service:通过Intent指定要启动的Service

2.conn:一个ServiceConnection对象，该对用用于监听访问者与Service之间的连接情况。当访问者与Service之间连接成功时将回调该ServiceConnection的onServiceConnectioned方法，当Service所在的宿主进程终止，导致Service与访问者之间断开连接的时回调该ServiceConnection的onServiceDesconnected方法

3.flags:指定绑定时是否自动创建Service（如果该Service还没有创建）。可指定为0（不自动创建），BIND_AUTO_CREATE（自动创建）。

         Activity传值给Service

MainActivity.java

package com.example.servicedemo;

import com.example.servicedemo.MyService.MyBinder;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity implements OnClickListener {

    private Button start_service_button, stop_service_button, bind_service_button, unbind_service_button,
            pass_on_message;
    private TextView tvOut;

    private Intent intent;

    private MyBinder myBinder;

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

        start_service_button = (Button) findViewById(R.id.start_service_button);
        stop_service_button = (Button) findViewById(R.id.stop_service_button);
        bind_service_button = (Button) findViewById(R.id.bind_service_button);
        unbind_service_button = (Button) findViewById(R.id.unbind_service_button);
        pass_on_message = (Button) findViewById(R.id.pass_on_message);
        tvOut = (TextView) findViewById(R.id.tvOut);

        start_service_button.setOnClickListener(this);
        stop_service_button.setOnClickListener(this);
        bind_service_button.setOnClickListener(this);
        unbind_service_button.setOnClickListener(this);
        pass_on_message.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.start_service_button:
            start();
            break;
        case R.id.stop_service_button:
            stop();
            break;
        case R.id.bind_service_button:
            bind();
            break;
        case R.id.unbind_service_button:
            unbind();
            break;
        case R.id.pass_on_message:
            passOnMessage();
            break;

        }
    }

    // 传递数据
    private void passOnMessage() {
        myBinder.setData("BBBBB");

    }

    // 解除绑定Service
    private void unbind() {
        Intent intent = new Intent(this, MyService.class);
        Log.d("TTTT", "===========点击了unbind按钮============");
        unbindService(conn);
    }

    // 绑定启动service
    private void bind() {
        Intent intent = new Intent(this, MyService.class);
        Log.d("TTTT", "===========点击了bind按钮============");
        bindService(intent, conn, BIND_AUTO_CREATE);
    }

    // 使用stopService关闭Service
    private void stop() {
        Intent intent = new Intent(this, MyService.class);
        Log.d("TTTT", "===========点击了stop按钮============");
        stopService(intent);
    }

    // 使用startService启动Service
    private void start() {
        Intent intent = new Intent(this, MyService.class);
        Log.d("TTTT", "===========点击了start按钮============");
        startService(intent);

    }

    ServiceConnection conn = new ServiceConnection() {

        @Override
        public void onServiceDisconnected(ComponentName name) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            myBinder = (MyBinder) service;

        }
    };
}

MyService.java

package com.example.servicedemo;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

public class MyService extends Service {

    private String data = "AAAAA";

    @Override
    public IBinder onBind(Intent intent) {
        Log.d("TTTT", "IBind方法运行了...");
        return new MyBinder();
    }

    @Override
    public void onCreate() {
        Log.d("TTTT", "onCreate方法运行了...");
        new Thread(new Runnable() {
            @Override
            public void run() {
                int j = 0;

                for (int i = 0; i < 30; i++) {
                    try {
                        j++;

                        String str = j + ":" + data;
                        Log.d("TTTT", str);

                        Thread.sleep(1000 * 1);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        }).start();
        super.onCreate();
    }

    @Override
    public void onStart(Intent intent, int startId) {
        // TODO Auto-generated method stub
        super.onStart(intent, startId);
        Log.d("TTTT", "onStart方法运行了...");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        Log.d("TTTT", "onStartCommand方法运行了...");

        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d("TTTT", "onDestroy方法运行了...");
    }

    @Override
    public boolean onUnbind(Intent intent) {
        Log.d("TTTT", "onUnbind方法运行了...");
        return super.onUnbind(intent);
    }

    public class MyBinder extends Binder {
        public void setData(String str) {
            data = str;
        }

        public MyService getService() {
            return MyService.this;
        }
    }
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.servicedemo.MainActivity" >

    <TextView
        android:id="@+id/tvOut"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/start_service_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="开启服务" />

    <Button
        android:id="@+id/stop_service_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="关闭服务" />

    <Button
        android:id="@+id/bind_service_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="绑定服务" />

    <Button
        android:id="@+id/unbind_service_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="解除绑定" />

    <Button
        android:id="@+id/pass_on_message"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="传递数据" />

</LinearLayout>

         Service传值给Activity

MainActivity.java

package com.example.passupmessageforservice;

import com.example.passupmessageforservice.MyService.Callback;
import com.example.passupmessageforservice.MyService.MyBinder;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity implements OnClickListener {

    private Button bt_bindService, bt_unbindService, bt_sync;
    private TextView showtext;
    private EditText et_str;

    private Intent intent;

    private MyBinder myBinder;

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

        initView();

        bt_bindService.setOnClickListener(this);
        bt_unbindService.setOnClickListener(this);
        bt_sync.setOnClickListener(this);
    }

    // 初始化view组件
    private void initView() {
        bt_bindService = (Button) findViewById(R.id.bt_bindService);
        bt_unbindService = (Button) findViewById(R.id.bt_unbindService);
        bt_sync = (Button) findViewById(R.id.bt_sync);
        showtext = (TextView) findViewById(R.id.showtext);
        et_str = (EditText) findViewById(R.id.et_str);
    }

    // 响应点击事件
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.bt_bindService:
            bind();
            break;
        case R.id.bt_unbindService:
            unbind();
            break;
        case R.id.bt_sync:
            sync();
            break;
        }
    }

    // 绑定服务
    private void bind() {
        Log.d("TTTT", "=========执行bind方法=========");
        intent = new Intent(this, MyService.class);
        bindService(intent, conn, BIND_AUTO_CREATE);
    }

    // 解除绑定
    private void unbind() {
        Log.d("TTTT", "=========执行unbind方法=========");
        unbindService(conn);
    }

    // 同步数据方法
    private void sync() {
        myBinder.setData(et_str.getText().toString());
    }

    ServiceConnection conn = new ServiceConnection() {

        @Override
        public void onServiceDisconnected(ComponentName name) {
            Log.d("TTTT", "=========执行onServiceDisconnected方法=========");

        }

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            Log.d("TTTT", "=========执行onServiceConnected方法=========");
            myBinder = (MyBinder) service;
            myBinder.getService().setCallback(new Callback() {

                public void change(String str) {
                    Log.d("TTTT", "~~~~~");
                    Message msg = new Message();
                    msg.obj = str;
                    handler.sendMessage(msg);
                }
            });
        }
    };

    Handler handler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            String str = (String) msg.obj;
            showtext.setText(str);
        };
    };

}

MyService.java

package com.example.passupmessageforservice;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

public class MyService extends Service {

    private String logStr = "AAAA";

    private Callback callback = null;

    private boolean status = false;

    @Override
    public IBinder onBind(Intent intent) {
        Log.d("TTTT", "~~~~~~~~~~~~执行onBind方法~~~~~~~~~~~~");
        return new MyBinder();
    }

    @Override
    public boolean onUnbind(Intent intent) {
        Log.d("TTTT", "~~~~~~~~~~~~执行onUnbind方法~~~~~~~~~~~~");
        status = true;
        return super.onUnbind(intent);
    }

    @Override
    public void onCreate() {
        super.onCreate();

        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < 15; i++) {
                    if (!status) {

                        if (callback != null) {
                            callback.change(i + ":" + logStr);
                            Log.d("TTTT", "================================");
                        }

                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                }
            }
        }).start();

        Log.d("TTTT", "~~~~~~~~~~~~执行onCreate方法~~~~~~~~~~~~");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d("TTTT", "~~~~~~~~~~~~执行onStartCommand方法~~~~~~~~~~~~");
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {

        Log.d("TTTT", "~~~~~~~~~~~~执行onDestroy方法~~~~~~~~~~~~");
        super.onDestroy();
    }

    public class MyBinder extends Binder {
        public void setData(String str) {
            logStr = str;
        }

        public MyService getService() {
            return MyService.this;
        }
    }

    public interface Callback {
        void change(String str);
    }

    public Callback getCallback() {
        return callback;
    }

    public void setCallback(Callback callback) {
        this.callback = callback;
    }

}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.passupmessageforservice.MainActivity" >

    <EditText
        android:id="@+id/et_str"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="输入要传入的文字" />

    <Button
        android:id="@+id/bt_bindService"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="绑定服务" />

    <Button
        android:id="@+id/bt_unbindService"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="解除绑定" />

    <Button
        android:id="@+id/bt_sync"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="同步数据" />

    <TextView
        android:id="@+id/showtext"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

Service的生命周期

Service的生命周期，从创建到销毁，有两条不同的路径。

         直接启动

使用startService()启动Service，初次启动会先调用onCreate()方法，然后调用onStartCommand()方法，创建Service之后，之后不会再调用onCreate()方法

这种Service可以无限的运行下去，必须调用stopSelf()方法或者其他组件调用stopService()方法来停止它

停止时会调用其onDestroy()方法来销毁这个Service

         绑定启动

被绑定的Service是当其他组件调用bindService来创建的

初次绑定会调用onCreate()方法，之后便不会再调用

紧接着会调用onBind()方法

当别的组件调用unbindService()时候，会调用Service的unbind方法，紧接着调用onDestroy()方法。