Android四大组件之广播接收器 Broadcast Receiver
2016-01-08 09:22
751 查看
对《第一行代码——android》的读书笔记
广播的类型:
1.标准广播:一种完全异步的广播,在广播发出后,所有的广播接收器几乎都会在同一时刻接收到这条广播消息,因此他们之间没有任何前后顺序可言。这种广播效率高,但是同时也意味着他是无法被截断的。
2.有序广播:一种同步执行的广播,同一时刻只有一个广播接收器能够收到这条广播。优先级高的会先收到这条广播,并且前面的广播接收器可以截断这条广播。
接收系统广播:
Android系统内置了许多系统级别的广播,比如电量的广播,位置信息变更的广播。接受这些广播就需要广播接收器。注册广播的形式一般有两种:动态在代码中注册或者在AndroidManifest.xml中注册。
广播接收器创建:
新建一个类继承BroadcastReceiver,并重写父类的onReceive()方法。当有广播到来,onReceive()方法就会得到执行,具体的逻辑就在这个方法中处理。我们的广播接收器想要监听什么广播,就相应的添加action
动态注册监听网络变化
调用registerReceiver()进行注册intentFilter=new IntentFilter(); intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE"); net=new NetworkChangeReceiver(); registerReceiver(net, intentFilter);
class NetworkChangeReceiver extends BroadcastReceiver{ @Override public void onReceive(Context context, Intent intent) { // TODO Auto-generated method stub ConnectivityManager connectionManager=(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); NetworkInfo networkinfo=connectionManager.getActiveNetworkInfo(); if(networkinfo!=null&&networkinfo.isAvailable()){ Toast.makeText(context, "有网络", Toast.LENGTH_LONG).show(); }else{ Toast.makeText(context, "mei有网络", Toast.LENGTH_LONG).show(); } }
通过getSystemService得到ConnectivityManager的实例,这是一个系统服务类,专门用来管理网络连接。然后调用getActiveNetworkInfo得到networkinof实例,接着调用isAvailable就可以判断当前是否有网络
动态注册的广播接收器一定要取消注册才行
protected void onDestroy(){ super.onDestroy(); unregisterReceiver(net); }
静态注册实现了开机启动
动态注册的滚广播接收器可以自由的控制注册与注销,但有一个缺点,即必须在程序启动后才能接受到广播,所以需要静态注册。public class BootCompleteReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { Toast.makeText(context, "Boot Complete", Toast.LENGTH_LONG).show(); } }
<receiver android:name=".BootCompleteReceiver" > <intent-filter> <action android:name="android.intent.action.BOOT_COMPLETED" /> </intent-filter> </receiver>
所有静态注册的广播都在receiver中进行注册,通过android:name=".BootCompleteReceiver" 指定具体注册哪一个广播接收器,然后在《intent-filter>标签里加入想要接受的广播就行了。由于Android系统启动后会发出android.intent.action.BOOT_COMPLETED的广播,因此在这添加了相应的action
发送自定义广播
发送标准广播
Intent inten t=new intent("antion");
sendBroadcast(intent);
发送有序广播
intent intent =new intent("action");
sendOrderedBroadcast(intent,null);
截断广播 abortBroadcast();使用本地广播
使用这种机制的广播只能在应用程序的内部进行传递,并且广播接收器只能接受来自本应用程序发出的广播。public class MainActivity extends Activity { private IntentFilter intentFilter; private LocalReceiver localReceiver; private LocalBroadcastManager localBroadcastManager; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); localBroadcastManager = LocalBroadcastManager.getInstance(this); Button button = (Button) findViewById(R.id.button); button.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent( "com.example.broadcasttest.LOCAL_BROADCAST"); localBroadcastManager.sendBroadcast(intent); } }); intentFilter = new IntentFilter(); intentFilter.addAction("com.example.broadcasttest.LOCAL_BROADCAST"); localReceiver = new LocalReceiver(); localBroadcastManager.registerReceiver(localReceiver, intentFilter); } @Override protected void onDestroy() { super.onDestroy(); localBroadcastManager.unregisterReceiver(localReceiver); } class LocalReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { Toast.makeText(context, "received local broadcast", Toast.LENGTH_SHORT).show(); } } }
这是添加了LocalBroadcastManager对发送,注册 销毁进行了管理
需要注意的是:本地广播无法通过静态注册的方法来接受。
广播的最佳实践----实现强制下线功能
创建ActivityCollector类用于管理所有的活动
public class ActivityCollector { private static List<Activity> activities = new ArrayList<Activity>(); public static void addActivity(Activity activity) { activities.add(activity); } public static void removeActivity(Activity activity) { activities.remove(activity); } public static void finishAll() { for (Activity activity : activities) { if (!activity.isFinishing()) { activity.finish(); } } } }
创建BaseActivity类作为所有活动的父类
public class BaseActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ActivityCollector.addActivity(this); } @Override protected void onDestroy() { super.onDestroy(); ActivityCollector.removeActivity(this); } }
登录页面
public class LoginActivity extends BaseActivity { private SharedPreferences pref; private SharedPreferences.Editor editor; private EditText accountEdit; private EditText passwordEdit; private Button login; private CheckBox rememberPass; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.login); pref = PreferenceManager.getDefaultSharedPreferences(this); accountEdit = (EditText) findViewById(R.id.account); passwordEdit = (EditText) findViewById(R.id.password); rememberPass = (CheckBox) findViewById(R.id.remember_pass); login = (Button) findViewById(R.id.login); boolean isRemember = pref.getBoolean("remember_password", false); if (isRemember) { String account = pref.getString("account", ""); String password = pref.getString("password", ""); accountEdit.setText(account); passwordEdit.setText(password); rememberPass.setChecked(true); } login.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { String account = accountEdit.getText().toString(); String password = passwordEdit.getText().toString(); if (account.equals("admin") && password.equals("123456")) { editor = pref.edit(); if (rememberPass.isChecked()) { editor.putBoolean("remember_password", true); editor.putString("account", account); editor.putString("password", password); } else { editor.clear(); } editor.commit(); Intent intent = new Intent(LoginActivity.this, MainActivity.class); startActivity(intent); finish(); } else { Toast.makeText(LoginActivity.this, "account or password is invalid", Toast.LENGTH_SHORT).show(); } } }); } }
发送广播
public class MainActivity extends BaseActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button forceOffline = (Button) findViewById(R.id.force_offline);
forceOffline.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(
"com.example.broadcastbestpractice.FORCE_OFFLINE");
sendBroadcast(intent);
}
});
}
}
广播接收器类
public class ForceOfflineReceiver extends BroadcastReceiver { @Override public void onReceive(final Context context, Intent intent) { AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(context); dialogBuilder.setTitle("Warning"); dialogBuilder .setMessage("You are forced to be offline. Please try to login again."); dialogBuilder.setCancelable(false);//对话框设置为不可取消 dialogBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { ActivityCollector.finishAll(); Intent intent = new Intent(context, LoginActivity.class); intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);//在广播接收其中必须加入加入一个标志 context.startActivity(intent); } }); AlertDialog alertDialog = dialogBuilder.create(); alertDialog.getWindow().setType( WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);//设置类型 保证在接受器中可以弹出 alertDialog.show(); } }
进行权限设置和注册
弹出一个系统级别的对话框,必须声明 <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
并制定接受
<receiver android:name=".ForceOfflineReceiver" >
<intent-filter>
<action android:name="com.example.broadcastbestpractice.FORCE_OFFLINE" />
</intent-filter>
</receiver>
相关文章推荐
- Android项目结构介绍
- Camera进阶,自定义拍照录像界面
- android windows 上JNI编程
- 怎样在Android项目中在一个数据库里建立多张表
- Android Studio 推荐的字体配置
- android学习日记(七):ViewPager+Fragment
- Android studio的安装
- 《Android源码设计模式解析与实战》读书笔记(十七)
- android_定义多个Activity及跳转
- android的RadioButton切换不同的fragment
- Android笔记(七十四) 详解Intent
- Android开发之常用Intent.Action【转】
- Android之Volley 源码解析
- Android之滑动事件冲突解决 Touch事件处理机制总结
- Android之DrawText详解
- Android Developer:合并清单文件
- AndroidStudio配置AndroidAnnotations
- OS X 上利用 Homebrew 安装 Android SDK
- Android开发-无法新建Activity及新建后编译错误
- How to see output from Android test