Android菜鳥練習第二十二課 Broadcast的基本使用

1.通過靜態方法註冊的接收者

public class FirstReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        String content = intent.getStringExtra("msg");
        Toast.makeText(context,content,Toast.LENGTH_SHORT).show();
    }

2.Manifest文件中application路徑下添加如下代碼

//靜態註冊爲常駐型，也就是說當應用關閉後，如果有廣播信息傳來，MyReceiver也會被系統調用而自動運行

<receiver android:name=".FirstReceiver">
    <intent-filter>
        <action android:name="android.intent.action.MY_BROADCAST"/>//發送廣播時的頻道
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
</receiver>

3.動態註冊的廣播接收者

public class SecondReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        String content = intent.getStringExtra("MSG");
        Toast.makeText(context,content,Toast.LENGTH_SHORT).show();
    }

}

4.activity中的代碼

public class MainActivity extends AppCompatActivity {
    SecondReceiver secondReceiver;

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

        findViewById(R.id.btn_first).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent();
                intent.setAction("android.intent.action.MY_BROADCAST");
                intent.putExtra("msg","這是第靜態註冊的廣播信息");
                sendBroadcast(intent);
            }
        });

        //動態註冊廣播
        secondReceiver = new SecondReceiver();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("android.intent.action.SECOND_BROADCAST");
        registerReceiver(secondReceiver,intentFilter);

        findViewById(R.id.btn_second).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("android.intent.action.SECOND_BROADCAST");
                intent.putExtra("MSG","這是動態註冊廣播接收到的消息");
                sendBroadcast(intent);
            }
        });
    }

    //動態註冊廣播當activity或者service銷燬時沒有接觸註冊系統會報異常
    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(secondReceiver);
    }
}

5.佈局中文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/btn_first"
        android:layout_width="match_parent"
        android:layout_height="45dp"
        android:text="向FirstReceiver發送消息" />

    <Button
        android:id="@+id/btn_second"
        android:layout_width="match_parent"
        android:layout_height="45dp"
        android:text="向SecondReceiver發送第一個消息" />

</LinearLayout>