在 Android 中使用 Activity, Service, Broadcast, BroadcastReceiver

介绍
在 Android 中使用 Activity, Service, Broadcast, BroadcastReceiver
活动(Activity) - 用于表现功能 
服务(Service) - 相当于后台运行的 Activity
广播(Broadcast) - 用于发送广播 
广播接收器(BroadcastReceiver) - 用于接收广播
Intent - 用于连接以上各个组件，并在其间传递消息  


1、演示 Activity 的基本用法，一个 Activity 启动另一个 Activity，启动另一个 Activity 时为其传递参数，被启动的 Activity 返回参数给启动者的 Activity

Main.java

代码 
package com.webabcd.activity;

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

public class Main extends Activity {
    
    TextView txt;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.main);

        txt = (TextView) this.findViewById(R.id.txt);
        txt.setText("Activity 1");

        Button btn = (Button) this.findViewById(R.id.btn);
        btn.setText("启动另一个Activity");
        btn.setOnClickListener(new Button.OnClickListener() {
            @Override
            public void onClick(View v) {
                
                // 实例化 Intent，指定需要启动的 Activity
                Intent intent = new Intent();
                intent.setClass(Main.this, MyActivity.class);

                // 实例化 Bundle，设置需要传递的参数
                Bundle bundle = new Bundle();
                bundle.putString("name", "webabcd");
                bundle.putDouble("salary", 100.13);

                // 将需要传递的参数赋值给 Intent 对象
                intent.putExtras(bundle);

                // startActivity(intent); // 启动指定的 Intent（不等待返回结果）
                // Main.this.finish();
                
                // 启动指定的 Intent，并等待返回结果
                // 其中第二个参数如果大于等于零，则返回结果时会回调 onActivityResult() 方法
                startActivityForResult(intent, 0);
            }
        });
        
        Log.d("MyDebug", "onCreate");
    }
    
    // 被启动的 Activity 返回结果时的回调函数
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (resultCode == Activity.RESULT_OK){
            Bundle bundle = data.getExtras();
            
            String name = bundle.getString("name");
            double salary = bundle.getDouble("salary");
            
            txt.setText("Activity 1" + "\n名字：" + name + "\n薪水：" + String.valueOf(salary));
        }
    }

    @Override
    protected void onStart() {
        // TODO Auto-generated method stub
        super.onStart();
        
        Log.d("MyDebug", "onStart");
    }

    @Override
    protected void onStop() {
        // TODO Auto-generated method stub
        super.onStop();
        
        Log.d("MyDebug", "onStop");
    }

    @Override
    protected void onRestart() {
        // TODO Auto-generated method stub
        super.onRestart();
        
        Log.d("MyDebug", "onRestart");
    }
    
    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        
        Log.d("MyDebug", "onPause");
    }

    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        
        Log.d("MyDebug", "onResume");
    }
    
    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        
        Log.d("MyDebug", "onDestroy");
    }
}

MyActivity.java

代码 
package com.webabcd.activity;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

// 被另一个 Activity 所启动的 Activity
public class MyActivity extends Activity {
    
    Intent intent;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.main2);

        // 获取启动者传递过来的参数
        intent = this.getIntent();
        Bundle bundle = intent.getExtras();        
        String name = bundle.getString("name");
        double salary = bundle.getDouble("salary");
        
        TextView txt = (TextView) this.findViewById(R.id.txt);
        txt.setText("Activity 2" + "\n名字：" + name + "\n薪水：" + String.valueOf(salary));

        Button btn = (Button) this.findViewById(R.id.btn);
        btn.setText("返回前一个Activity");
        btn.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                // 返回参数给启动者
                MyActivity.this.setResult(Activity.RESULT_OK, intent);
                MyActivity.this.finish();
            }
        });
    }
}


AndroidManifest.xml

代码 
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.webabcd.activity" android:versionCode="1"
    android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Main" android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <!--
            如果有需要用到的 Activity ，则都要在这里做相应的配置
        -->
        <activity android:name=".MyActivity" android:label="Activity 2" />
    </application>
    <uses-sdk android:minSdkVersion="3" />
</manifest> 


2、Service, Broadcast, BroadcastReceiver 的演示
Main.java

代码 
package com.webabcd.service;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;

/*
 * startService() 和 bindService() 的区别 
 * startService() - 正常理解就好
 * bindService() - 使当前上下文对象（本例中就是 Activity）通过一个 ServiceConnection 对象邦定到指定的 Service 。这样，如果上下文对象销毁了的话，那么其对应的 Service 也会被销毁
 */
public class Main extends Activity implements OnClickListener {

    private TextView txtMsg;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        setTitle("android 之 service");

        this.findViewById(R.id.btnStart).setOnClickListener(this);
        this.findViewById(R.id.btnStop).setOnClickListener(this);
        this.findViewById(R.id.btnBind).setOnClickListener(this);
        this.findViewById(R.id.btnUnbind).setOnClickListener(this);
        
        txtMsg = (TextView)this.findViewById(R.id.txtMsg);
        
        // 实例化自定义的 BroadcastReceiver
        receiver = new UpdateReceiver();
        IntentFilter filter = new IntentFilter();
        // 为 BroadcastReceiver 指定 action ，使之用于接收同 action 的广播
        filter.addAction("com.webabcd.service.msg");
        
        // 以编程方式注册  BroadcastReceiver 。配置方式注册 BroadcastReceiver 的例子见 AndroidManifest.xml 文件
        // 一般在 OnStart 时注册，在 OnStop 时取消注册
        this.registerReceiver(receiver, filter);
        // this.unregisterReceiver(receiver);
        
    }

    @Override
    public void onClick(View v) {
        Intent intent = new Intent(Main.this, MyService.class);
        switch (v.getId()) {
        case R.id.btnStart:
            this.startService(intent);
            break;
        case R.id.btnStop:
            this.stopService(intent);
            break;
        case R.id.btnBind:
            this.bindService(intent, conn, Context.BIND_AUTO_CREATE);
            break;
        case R.id.btnUnbind:
            this.unbindService(conn);
            break;
        }
    }

    // bindService() 所需的 ServiceConnection 对象
    private ServiceConnection conn = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName className, IBinder service) {
            
        }
        @Override
        public void onServiceDisconnected(ComponentName className) {
            
        }
    };
    
    private String msg="";
    private UpdateReceiver receiver;
    // 实现一个 BroadcastReceiver，用于接收指定的 Broadcast
    public class UpdateReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            msg = intent.getStringExtra("msg");
            
            txtMsg.append(msg + "\n");
        }
        
    }
}

MyService.java

代码 
package com.webabcd.service;

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

// 演示 Service 的生命周期。具体信息运行程序后在 LogCat 中查看
public class MyService extends Service {

    @Override
    public IBinder onBind(Intent intent) {
        
        Log.d("MyDebug", "onBind");
        sendMsg("onBind");
        
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void onCreate() {
        // TODO Auto-generated method stub
        super.onCreate();
        
        Log.d("MyDebug", "onCreate");
        sendMsg("onCreate");
    }

    @Override
    public void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        
        Log.d("MyDebug", "onDestroy");
        sendMsg("onDestroy");
    }

    @Override
    public void onRebind(Intent intent) {
        // TODO Auto-generated method stub
        super.onRebind(intent);
        
        Log.d("MyDebug", "onRebind");
        sendMsg("onRebind");
    }

    @Override
    public void onStart(Intent intent, int startId) {
        super.onStart(intent, startId);
        
        Log.d("MyDebug", "onStart");
        sendMsg("onStart");
    }
    
    @Override
    public boolean onUnbind(Intent intent) {
        
        Log.d("MyDebug", "onUnbind");
        sendMsg("onUnbind");
        
        // TODO Auto-generated method stub
        return super.onUnbind(intent);
    }
    
    // 发送广播信息
    private void sendMsg(String msg){
        // 指定广播目标的 action （注：指定了此 action 的 receiver 会接收此广播）
        Intent intent = new Intent("com.webabcd.service.msg");
        // 需要传递的参数
        intent.putExtra("msg", msg);
        // 发送广播
        this.sendBroadcast(intent);
    }
}


MyBootReceiver.java

代码 
package com.webabcd.service;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

public class MyBootReceiver extends BroadcastReceiver {

    // 用于接收满足条件的 Broadcast（相应的 Broadcast 的注册信息详见 AndroidManifest.xml ，当系统启动完毕后会调用这个广播接收器）
    @Override
    public void onReceive(Context arg0, Intent arg1) {
        Log.d("MyDebug", "onReceive");
        
        // 启动服务
        Intent service = new Intent(arg0, MyService.class);
        arg0.startService(service);
    }

}


AndroidManifest.xml

代码 
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.webabcd.service" android:versionCode="1"
    android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Main" android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <!--
            如果有需要用到的 service ，则都要在这里做相应的配置
        -->
        <service android:name=".MyService"></service>
        
        <!--
            注册一个 BroadcastReceiver
            其 intent-filter 为 android.intent.action.BOOT_COMPLETED（用于接收系统启动完毕的 Broadcast）
        -->
        <receiver android:name=".MyBootReceiver">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>
    </application>
    
    <!--
        接受系统启动完毕的 Broadcast 的权限
    -->
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    <uses-sdk android:minSdkVersion="3" />
</manifest> 


OK