BroadcastReceiver:无法实例化类; 没有空的构造函数

Question

我有内部类作为广播接收器:

public class ManualBacklightReceiver extends BroadcastReceiver {

    public static final String ACTION_MANUAL_BACKLIGHT = "com.android.systemui.statusbar.powerwidget.MANUAL_BACKLIGHT";

    public ManualBacklightReceiver() {
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.d("ManualBacklightReceiver", intent.getAction());
    }

};

AndroidManifest:

<receiver android:name=".statusbar.powerwidget.PowerWidgetGrid$ManualBacklightReceiver">
        <intent-filter>
            <action android:name="com.android.systemui.statusbar.powerwidget.MANUAL_BACKLIGHT"/>
        </intent-filter>            
    </receiver>

当我用这段代码发送意图时:Intent intent = new Intent();

intent.setAction("com.android.systemui.statusbar.powerwidget.MANUAL_BACKLIGHT");
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
mContext.sendBroadcast(intent);

我得到以下例外:

java.lang.RuntimeException: Unable to instantiate receiver com.android.systemui.statusbar.powerwidget.PowerWidgetGrid$ManualBacklightReceiver:
java.lang.InstantiationException: can't instantiate class com.android.systemui.statusbar.powerwidget.PowerWidgetGrid$ManualBacklightReceiver; no empty constructor
Caused by: java.lang.InstantiationException: can't instantiate class com.android.systemui.statusbar.powerwidget.PowerWidgetGrid$ManualBacklightReceiver; no empty constructor

但我有一个空的构造函数!为什么它不起作用？

Answer 1

您需要将内部类声明为静态.否则,内部类与外部类的实例相关联.

有关详细信息,请查看Java嵌套类教程.这是一个片段:

InnerClass的实例只能存在于OuterClass的实例中,并且可以直接访问其封闭实例的方法和字段.下图说明了这个想法.

和:

嵌套类是其封闭类的成员.非静态嵌套类(内部类)可以访问封闭类的其他成员,即使它们被声明为私有.静态嵌套类无权访问封闭类的其他成员.作为OuterClass的成员,可以将嵌套类声明为private,public,protected或package private.(回想一下,外部类只能声明为public或package private.)