Android- 活动(Activity), 服务(Service), 广播(Broadcast), 广播接收器(BroadcastReceiver)

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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
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

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
<?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
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
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
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
<?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>

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