1、广播

广播包括发广播和广播接收者

1.1、监听电量变化的广播

public class MainActivity extends AppCompatActivity {

    private TextView mBatteryLevel;

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

    }

    private void initView() {
        mBatteryLevel = this.findViewById(R.id.battery_level);

    }

    private void registerBatteryReceiver() {
        //2. 要收听的频道：电量变化
        IntentFilter intentFilter = new IntentFilter();
        //3. 设置频道
        intentFilter.addAction(Intent.ACTION_BATTERY_CHANGED);
        //4.创建对象
        BatteryStatusReceiver receiver = new BatteryStatusReceiver();
        //5.完成注册广播（动态注册）
        this.registerReceiver(receiver,intentFilter);
    }


    /**
     * 1.创建广播接收者，继承自BroadcastReceiver
     */
    public class BatteryStatusReceiver extends BroadcastReceiver {
        private static final String TAG = "BatteryStatusReceiver";

        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            Log.d(TAG, "action is == " + action);
            //监听电量的变化，同时为了防止空指针异常
            if(mBatteryLevel != null){
                mBatteryLevel.setText("当前电量："  + intent.getIntExtra(BatteryManager.EXTRA_LEVEL,0));
            }

            //计算电量百分比
            int maxLevel = intent.getIntExtra(BatteryManager.EXTRA_SCALE, 0);
            int currentLevel = intent.getIntExtra(BatteryManager.EXTRA_LEVEL,0);
            float percent = currentLevel * 1.0f / maxLevel * 100;
            Log.d(TAG, "当前电量比为：" + percent + "%");
        }
    }
}

注意权限：

1.2、监听USB线拔出和插入

在这里插入图片描述

//3. 设置频道
intentFilter.addAction(Intent.ACTION_BATTERY_CHANGED);
//USB插入
intentFilter.addAction(Intent.ACTION_POWER_CONNECTED);
//USB拔出
intentFilter.addAction(Intent.ACTION_POWER_DISCONNECTED);

public class BatteryStatusReceiver extends BroadcastReceiver {
        private static final String TAG = "BatteryStatusReceiver";

        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (Intent.ACTION_BATTERY_CHANGED.equals(action)) {
                Log.d(TAG, "action is == " + action);
                //监听电量的变化，同时为了防止空指针异常
                if(mBatteryLevel != null){
                    mBatteryLevel.setText("当前电量："  + intent.getIntExtra(BatteryManager.EXTRA_LEVEL,0));
                }

                //计算电量百分比
                int maxLevel = intent.getIntExtra(BatteryManager.EXTRA_SCALE, 0);
                int currentLevel = intent.getIntExtra(BatteryManager.EXTRA_LEVEL,0);
                float percent = currentLevel * 1.0f / maxLevel * 100;
                Log.d(TAG, "当前电量比为：" + percent + "%");
            } else if(Intent.ACTION_POWER_CONNECTED.equals(action)){
                Log.d(TAG, "usb连接");
            } else if(Intent.ACTION_POWER_DISCONNECTED.equals(action)){
                Log.d(TAG, "usb断开");
            }

        }
    }

1.3、取消注册

private void registerBatteryReceiver() {
        //2. 要收听的频道：电量变化
        IntentFilter intentFilter = new IntentFilter();
        //3. 设置频道
        intentFilter.addAction(Intent.ACTION_BATTERY_CHANGED);
        //USB插入
        intentFilter.addAction(Intent.ACTION_POWER_CONNECTED);
        //USB拔出
        intentFilter.addAction(Intent.ACTION_POWER_DISCONNECTED);
        //4.创建广播接收者
        mReceiver = new BatteryStatusReceiver();
        //5.完成注册广播
        this.registerReceiver(mReceiver,intentFilter);
    }

@Override
    protected void onDestroy() {
        super.onDestroy();
        //取消广播注册
        if (mReceiver != null) {
            this.unregisterReceiver(mReceiver);
        }
    }

1.4、静态注册监听开机广播

这里推荐使用动态注册。

从 Android 8.0（API 级别 26）开始，系统对清单声明的接收器施加了额外的限制。
如果您的应用以 Android 8.0 或更高版本为目标平台，那么对于大多数隐式广播（没有明确针对您的应用的广播），您不能使用清单来声明接收器。当用户正在活跃地使用您的应用时，您仍可使用上下文注册的接收器。

创建广播接收者

public class BootCompleteRecevicer extends BroadcastReceiver {

    private static final String TAG = "BootCompleteRecevicer";

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        Log.d(TAG, "action " + action);
        Log.d(TAG, "开机完成");
        Toast.makeText(context,"收到开机完成的广播", Toast.LENGTH_SHORT).show();
    }
}

        <receiver android:name=".BootCompleteRecevicer">
<!--            第二步：与动态注册设置action是一样的-->
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
        </receiver>
    </application>

权限
在这里插入图片描述

1.5、监听应用于安装

监听应用的安装与卸载目的是为了收集信息。

<receiver android:name=".AppStateChangeReceiver">
            <intent-filter>
<!--                应用安装与卸载-->
                <action android:name="android.intent.action.PACKAGE_ADDED"/>
                <action android:name="android.intent.action.PACKAGE_REMOVED"/>

                <data android:scheme="package"/>
            </intent-filter>
        </receiver>

public class AppStateChangeReceiver extends BroadcastReceiver {
    private static final String TAG = "AppStateChangeReceiver";

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (action.equals(Intent.ACTION_PACKAGE_ADDED)) {
            //应用安装
            Log.d(TAG, "应用安装了，信息是 " + intent.getData());
        }else if(action.equals(Intent.ACTION_PACKAGE_REMOVED)){
            //应用卸载
            Log.d(TAG, "应用卸载了，信息是 " + intent.getData());
        }
    }
}

1.6、自定义广播和接收

创建广播发送者

public class SendBroadcastActivity extends Activity {

    private EditText mInputBox;

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

    private void initView() {
        mInputBox = this.findViewById(R.id.msg_et);
    }

    //该方法被点击就被调用
    public void sendBroadcastMsg(View view){
        //发广播
        String inputContent = mInputBox.getText().toString();
        Intent intent = new Intent();
        intent.setAction(Constans.ACTION_SEND_MSG);
        intent.putExtra(Constans.KEY_CONTENT, inputContent);
        //发送广播
        sendBroadcast(intent);
    }
}

创建广播接收者

public class MessageReceiver extends BroadcastReceiver {
    private static final String TAG = "MessageReceiver";

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        Log.d(TAG, "action is " + action);
        String content = intent.getStringExtra(Constans.KEY_CONTENT);
        Log.d(TAG, "content is " + content);
    }
}

注册

<activity android:name=".SendBroadcastActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver android:name=".MessageReceiver">
            <intent-filter>
                <action android:name="com.example.broadcastdemo.SENGD_MSG"/>
            </intent-filter>
        </receiver>

1.7、广播接收者之有序广播的发送

不是重点

<receiver android:name=".SchoolReceiver">
    <!--优先级是1000~-1000之间,超出了范围则会使用边界值,默认值为0-->
    <intent-filter android:priority="1000">
        <action android:name="com.sunofbeaches.broadcastdemo.DONATION"/>
    </intent-filter>
</receiver>

<receiver android:name=".GradeReceiver">
    <intent-filter android:priority="500">
        <action android:name="com.sunofbeaches.broadcastdemo.DONATION"/>
    </intent-filter>
</receiver>


<receiver android:name=".ClassReceiver">
    <intent-filter android:priority="100">
        <action android:name="com.sunofbeaches.broadcastdemo.DONATION"/>
    </intent-filter>
</receiver>


<receiver android:name=".PoorStudentReceiver">
    <intent-filter android:priority="-1000">
        <action android:name="com.sunofbeaches.broadcastdemo.DONATION"/>
    </intent-filter>
</receiver>