4. 泄漏根因分类：未解绑、静态内部类隐式持有、匿名内部类、单例持有Context

动态注册的 BroadcastReceiver 泄漏，本质上都是 Activity / Context 引用被外部对象长周期持有，导致生命周期结束时无法回收。根据引用持有方式的不同，可归纳为以下四类根因：

4.1 未解绑（Missing unregisterReceiver）

// ❌ 错误示例：注册后没有对应的解绑
@Override
protected void onResume() {
    super.onResume();
    IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
    registerReceiver(mBatteryReceiver, filter);
    // 漏掉了 onPause 中的 unregisterReceiver
}

// ✅ 正确示例：onPause 中解绑
@Override
protected void onResume() {
    super.onResume();
    IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
    registerReceiver(mBatteryReceiver, filter);
}

@Override
protected void onPause() {
    super.onPause();
    unregisterReceiver(mBatteryReceiver);
}

4.2 静态内部类隐式持有

当 BroadcastReceiver 被定义为 static inner class 时，它本身不持有外部 Activity 引用。但若该静态内部类中使用了外部类的成员变量（如 TextView、View），则会隐式地持有外部类的 this 引用，导致 Activity 无法 GC。

// ❌ 错误：静态内部类访问了外部 Activity 的字段（形成隐式持有）
public class MainActivity extends Activity {
    private TextView mStatusText;

    static class MyReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            // 实际持有 MainActivity.this
            mStatusText.setText("Received");
        }
    }
}

// ✅ 修复：使用 WeakReference 解除强引用
public class MainActivity extends Activity {
    private TextView mStatusText;

    static class MyReceiver extends BroadcastReceiver {
        private WeakReference textRef;
        MyReceiver(TextView tv) { textRef = new WeakReference<>(tv); }

        @Override
        public void onReceive(Context context, Intent intent) {
            TextView tv = textRef.get();
            if (tv != null) tv.setText("Received");
        }
    }
}

4.3 匿名内部类

在 registerReceiver 中直接 new BroadcastReceiver() {...} 创建的匿名内部类会隐式地持有外部 Activity 的引用。如果该 Receiver 被注册为 静态变量 或 持久化的成员变量，则会导致泄漏。

// ❌ 错误：匿名内部类 + 静态变量持有导致泄漏
public class MainActivity extends Activity {
    private static BroadcastReceiver sReceiver; // 静态变量长生命周期

    @Override
    protected void onResume() {
        super.onResume();
        sReceiver = new BroadcastReceiver() {  // 匿名内部类持有 MainActivity.this
            @Override
            public void onReceive(Context context, Intent intent) {
                // do something
            }
        };
        registerReceiver(sReceiver, new IntentFilter("com.example.CUSTOM"));
    }

    @Override
    protected void onPause() {
        super.onPause();
        // 如果有解绑，但 sReceiver 仍被静态变量持有
        unregisterReceiver(sReceiver);
    }
    // 即使解绑，静态变量仍引用了这个匿名 Receiver 对象，阻止其回收
}

// ✅ 修复：避免静态变量；或使用非匿名类并在 onDestroy 中置 null
public class MainActivity extends Activity {
    private BroadcastReceiver mReceiver;

    @Override
    protected void onResume() {
        super.onResume();
        mReceiver = new MyReceiver();
        registerReceiver(mReceiver, new IntentFilter("com.example.CUSTOM"));
    }

    @Override
    protected void onPause() {
        super.onPause();
        unregisterReceiver(mReceiver);
        mReceiver = null; // 帮助 GC
    }

    private static class MyReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) { }
    }
}

4.4 单例持有 Context

单例模式中持有 Activity 类型的 Context，会使 Activity 及其关联的 BroadcastReceiver 永远无法被回收。这是最常见且影响最严重的泄漏类型。

// ❌ 错误：单例持有 Activity Context
public class NetworkManager {
    private static NetworkManager sInstance;
    private Context mContext;

    private NetworkManager(Context context) {
        mContext = context; // 如果传入的是 Activity，则 Activity 泄漏
    }

    public static NetworkManager getInstance(Context context) {
        if (sInstance == null) sInstance = new NetworkManager(context);
        return sInstance;
    }

    public void registerNetworkReceiver() {
        IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
        mContext.registerReceiver(new NetworkReceiver(), filter);
    }
}

// ✅ 修复：单例使用 Application Context
public class NetworkManager {
    private static NetworkManager sInstance;
    private Context mAppContext;

    private NetworkManager(Context context) {
        mAppContext = context.getApplicationContext(); // 安全
    }

    // ...
}

四类泄漏根因对比速查表