Android：广播的使用实例

说明
首次发布	2019年02月15日
最近更新	2019年02月15日

广播的生命周期

BroadcastReceiver生命周期只有十秒左右，如果在onReceive()内做超过十秒的事情，就会报错。所以广播中不要执行耗时操作，可以考虑启动一个Service来完成操作。

广播的分类

根据注册方式，可以分为静态广播和动态广播。

静态广播

需要在AndroidManifest.xml文件中配置，具有常驻性广播，无论程序启动与否，广播依然存在的特点。比如：我们可以接收开机的广播，当收到这条广播时就可以在 onReceive()方法里执行相应的逻辑，从而实现开机启动的功能。

由于谷歌从Android 8开始，对静态广播做了限制，具体请查看。需要在发送广播时，给intent添加setComponent()，ComponentName(@NonNull String pkg, @NonNull String cls)有两个参数：参数一为包名，参数二为接收器receiver在包内的路径。具体请参考代码。

动态广播

代码中动态指定广播地址并注册，具有非常驻型，广播会跟随程序的生命周期的结束而结束的特点。需要特别注意的是：需要在onCreate()中进行注册，在onDestroy()中进行注销。

---

AndroidManifest.xml

    <application
      ....
        <!--注册静态广播-->
        <receiver android:name=".other.DynamicBroadcastReceiver">
            <intent-filter>
                <action android:name="com.tencent.testand.StaticBroadcast"/>
            </intent-filter>
        </receiver>

    </application>

BroadcastActivity

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.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.content.LocalBroadcastManager;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.tencent.testand.R;
import com.tencent.testand.other.DynamicBroadcastReceiver;


public class BroadcastActivity extends Activity implements View.OnClickListener {

    public static final String DYNAMIC_BROADCAST_ACTION = "com.tencent.testand.DynamicBroadcast";
    public static final String STATIC_BROADCAST_ACTION = "com.tencent.testand.StaticBroadcast";
    public static final String LOCAL_BROADCAST = "my_local_broadcast";
    private Button mSendDynamicBroadcastButton;
    private DynamicBroadcastReceiver mReceiver;
    private Button mSendStaticBroadcastButton;
    private Button mSendLocalBroadcastButton;
    private LocalReceiver mLocalReceiver;
    private LocalBroadcastManager mLocalBroadcastManager;

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

        findViews();

        registerBroadcast();

        registerLocalBroadcast();
    }

    /**
     * 注册本地广播
     */
    private void registerLocalBroadcast() {
        mLocalBroadcastManager = LocalBroadcastManager.getInstance(this);
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(LOCAL_BROADCAST);
        mLocalReceiver = new LocalReceiver();
        mLocalBroadcastManager.registerReceiver(mLocalReceiver, intentFilter);
    }

    private void findViews() {
        mSendDynamicBroadcastButton = findViewById(R.id.send_dynamic_broadcast_button);
        mSendDynamicBroadcastButton.setOnClickListener(this);

        mSendStaticBroadcastButton = findViewById(R.id.send_static_broadcast_button);
        mSendStaticBroadcastButton.setOnClickListener(this);

        mSendLocalBroadcastButton = findViewById(R.id.send_local_broadcast_button);
        mSendLocalBroadcastButton.setOnClickListener(this);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        // 注销
        unregisterReceiver(mReceiver);

        // 注销本地广播
        mLocalBroadcastManager.unregisterReceiver(mLocalReceiver);
    }

    /**
     * 注册广播
     */
    private void registerBroadcast() {
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(DYNAMIC_BROADCAST_ACTION);

        mReceiver = new DynamicBroadcastReceiver();
        registerReceiver(mReceiver, intentFilter);
    }

    /**
     * 内部类：本地广播的接收者
     */
    public class LocalReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "received local broadcast",
                    Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.send_dynamic_broadcast_button: {
                // 注意：intent里面必须要写action的名字
                Intent intent = new Intent(DYNAMIC_BROADCAST_ACTION);
                intent.putExtra("key", "I'm dynamic broadcast");
                sendBroadcast(intent);
                break;
            }

            case R.id.send_static_broadcast_button: {
                // 注意：intent里面必须要写action的名字
                Intent intent = new Intent(STATIC_BROADCAST_ACTION);

                intent.setComponent(new ComponentName(getPackageName(), getPackageName() + ".other.DynamicBroadcastReceiver"));
                intent.putExtra("key", "I'm static broadcast");
                sendBroadcast(intent);
                break;
            }

            case R.id.send_local_broadcast_button: {
                // 注意：intent里面必须要写action的名字
                Intent intent = new Intent(LOCAL_BROADCAST);

                intent.putExtra("key", "I'm local broadcast");
                // 注意：这里一定要用mLocalBroadcastManager，这也是本地广播与其他广播的区别
                mLocalBroadcastManager.sendBroadcast(intent);
                break;
            }
        }
    }
}

DynamicBroadcastReceiver

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.text.TextUtils;
import android.util.Log;
import android.widget.Toast;

import com.tencent.testand.activity.DynamicBroadcastActivity;

public class DynamicBroadcastReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // 根据action来区分广播
        if (TextUtils.equals(intent.getAction(), DynamicBroadcastActivity.DYNAMIC_BROADCAST_ACTION)
                || TextUtils.equals(intent.getAction(), DynamicBroadcastActivity.STATIC_BROADCAST_ACTION))
        {
            Toast.makeText(context, intent.getStringExtra("key"), Toast.LENGTH_LONG).show();
            Log.i(getClass().getSimpleName(), "onReceive: ");
        }
    }
}