Android - 在静态内部 Activity 类中制作 toast 或对话

Question

我在获取 static 内部类中的应用程序上下文时遇到问题:

public class MainActivity extends Activity {
        .....
        ....

        public static class SMSAlertHandler extends BroadcastReceiver {
                @Override
                public void onReceive(Context context, Intent intent) {
                    ....
                    ....
                    Toast.makeText(context, "this is my Toast message!!! =)",
                               Toast.LENGTH_LONG).show();
                    }
                }
            }

如果我给出上下文它给出异常

Unable to add window — token null is not for an application

另外，如果我输入 getApplicationContext()，显示错误

Cannot make a static reference to the non-static method getApplicationContext() from the type ContextWrapper

Answer 1

是的，静态方法不能使用对非静态字段的引用。而你接收到你的receiver中的context是不允许进行UI操作的，你可以看看this article这显示了您可以对收到的每个上下文执行的操作。

您可以在 Activity 中设置接收器，如下所示:

protected void onResume() {
    super.onResume();
    IntentFilter filter = new IntentFilter("YourAction");
    registerReceiver(receiver, filter);
    // or LocalBroadcastManager.getInstance(this).registerReceiver(receiver, filter); if you are using LocalBroadcast system
} 



private BroadcastReceiver receiver = new BroadcastReceiver() {
     @Override
     public void onReceive(Context context, Intent intent) {
         Toast.makeText(MainActivity.this, "message", LENGHT_LONG).show();
     } 
}

还有第二种方法(我不确定是否可行，因为我还没有测试)但是在简历中你从应用程序类中获取上下文:

您可以创建一个应用程序类来获取上下文，示例:

public class App extends android.app.Application {

    private static android.app.Application application;

    public static Context getContext() {
        return application.getApplicationContext();
    }

    public void onCreate() {
        super.onCreate();
        application = this;
    }
}

然后您就可以在接收器内部使用:

public static class SMSAlertHandler extends BroadcastReceiver {
   @Override
   public void onReceive(Context context, Intent intent) {
        Toast.makeText(App.getContext(), "this is my Toast message!!! =)",
                               Toast.LENGTH_LONG).show();
        }
   }
}

记得将 App 类添加到您的 AndroidManifext.xml

<application
        android:name=".App"
        ... >