Question

我有两个类，一个是HomeActivity，第二个是AlarmReciever

在HomeActivity中创建的AlarmManager服务，它在一段指定的时间内调用AlarmReciver

现在我想要在调用AlarmReciver时显示一个对话框，它应该是在HomeActivity中定义

这是两个文件的源代码和LogCat

import android.os.Bundle;
import android.app.Activity;
import android.app.AlarmManager;
import android.app.Dialog;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;


public class HomeActivity extends Activity {

    private TextView textView;

    private PendingIntent pendingIntent;
    private AlarmManager manager;

    static Dialog dialog;

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

        Intent alarmIntent = new Intent(HomeActivity.this, AlarmReceiver.class);
        pendingIntent = PendingIntent.getBroadcast(this, 0, alarmIntent, 0);

        manager = (AlarmManager)getSystemService(Context.ALARM_SERVICE);
        int interval = 10000;

        manager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), interval, pendingIntent);
        Toast.makeText(this, "Antivirus Started", Toast.LENGTH_SHORT).show();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_home, menu);
        return true;
    }

        public void openDialog(){
        dialog = new Dialog(HomeActivity.this);
        dialog.setContentView(R.layout.ask_question);
    }
}

//这是第二类

import android.app.Dialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class AlarmReceiver extends BroadcastReceiver {
    Context c;
    @Override
    public void onReceive(Context arg0, Intent arg1) {

        HomeActivity home = new HomeActivity();
        home.openDialog();

    }
}

//和LogCat

10-27 19:51:40.645: D/dalvikvm(27137): Late-enabling CheckJNI
10-27 19:51:41.545: E/DATABASE(27137): SELECT  * FROM register
10-27 19:51:42.075: D/OpenGLRenderer(27137): Enabling debug mode 0
10-27 19:51:52.775: D/AndroidRuntime(27137): Shutting down VM
10-27 19:51:52.785: W/dalvikvm(27137): threadid=1: thread exiting with uncaught exception (group=0x41698c08)
10-27 19:51:52.795: E/AndroidRuntime(27137): FATAL EXCEPTION: main
10-27 19:51:52.795: E/AndroidRuntime(27137): Process: com.example.malwaredetection, PID: 27137
10-27 19:51:52.795: E/AndroidRuntime(27137): java.lang.RuntimeException: Unable to start receiver com.example.malwaredetection.AlarmReceiver: java.lang.NullPointerException
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2704)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.app.ActivityThread.access$1800(ActivityThread.java:179)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1400)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.os.Handler.dispatchMessage(Handler.java:102)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.os.Looper.loop(Looper.java:146)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.app.ActivityThread.main(ActivityThread.java:5641)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at java.lang.reflect.Method.invokeNative(Native Method)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at java.lang.reflect.Method.invoke(Method.java:515)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1288)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1104)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at dalvik.system.NativeStart.main(Native Method)
10-27 19:51:52.795: E/AndroidRuntime(27137): Caused by: java.lang.NullPointerException
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:166)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:103)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.app.Dialog.<init>(Dialog.java:159)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.app.Dialog.<init>(Dialog.java:136)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at com.example.malwaredetection.HomeActivity.openDialog(HomeActivity.java:87)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at com.example.malwaredetection.AlarmReceiver.onReceive(AlarmReceiver.java:15)
10-27 19:51:52.795: E/AndroidRuntime(27137):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2687)
10-27 19:51:52.795: E/AndroidRuntime(27137):    ... 10 more
10-27 19:52:55.735: D/AndroidRuntime(27939): Shutting down VM
10-27 19:52:55.735: W/dalvikvm(27939): threadid=1: thread exiting with uncaught exception (group=0x41698c08)
10-27 19:52:55.745: E/AndroidRuntime(27939): FATAL EXCEPTION: main
10-27 19:52:55.745: E/AndroidRuntime(27939): Process: com.example.malwaredetection, PID: 27939
10-27 19:52:55.745: E/AndroidRuntime(27939): java.lang.RuntimeException: Unable to start receiver com.example.malwaredetection.AlarmReceiver: java.lang.NullPointerException
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2704)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.app.ActivityThread.access$1800(ActivityThread.java:179)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1400)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.os.Handler.dispatchMessage(Handler.java:102)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.os.Looper.loop(Looper.java:146)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.app.ActivityThread.main(ActivityThread.java:5641)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at java.lang.reflect.Method.invokeNative(Native Method)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at java.lang.reflect.Method.invoke(Method.java:515)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1288)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1104)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at dalvik.system.NativeStart.main(Native Method)
10-27 19:52:55.745: E/AndroidRuntime(27939): Caused by: java.lang.NullPointerException
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:166)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:103)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.app.Dialog.<init>(Dialog.java:159)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.app.Dialog.<init>(Dialog.java:136)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at com.example.malwaredetection.HomeActivity.openDialog(HomeActivity.java:87)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at com.example.malwaredetection.AlarmReceiver.onReceive(AlarmReceiver.java:15)
10-27 19:52:55.745: E/AndroidRuntime(27939):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2687)
10-27 19:52:55.745: E/AndroidRuntime(27939):    ... 10 more
10-27 19:53:01.655: D/AndroidRuntime(28095): Shutting down VM
10-27 19:53:01.665: W/dalvikvm(28095): threadid=1: thread exiting with uncaught exception (group=0x41698c08)
10-27 19:53:01.735: E/AndroidRuntime(28095): FATAL EXCEPTION: main
10-27 19:53:01.735: E/AndroidRuntime(28095): Process: com.example.malwaredetection, PID: 28095
10-27 19:53:01.735: E/AndroidRuntime(28095): java.lang.RuntimeException: Unable to start receiver com.example.malwaredetection.AlarmReceiver: java.lang.NullPointerException
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2704)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.app.ActivityThread.access$1800(ActivityThread.java:179)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1400)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.os.Handler.dispatchMessage(Handler.java:102)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.os.Looper.loop(Looper.java:146)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.app.ActivityThread.main(ActivityThread.java:5641)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at java.lang.reflect.Method.invokeNative(Native Method)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at java.lang.reflect.Method.invoke(Method.java:515)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1288)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1104)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at dalvik.system.NativeStart.main(Native Method)
10-27 19:53:01.735: E/AndroidRuntime(28095): Caused by: java.lang.NullPointerException
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:166)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:103)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.app.Dialog.<init>(Dialog.java:159)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.app.Dialog.<init>(Dialog.java:136)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at com.example.malwaredetection.HomeActivity.openDialog(HomeActivity.java:87)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at com.example.malwaredetection.AlarmReceiver.onReceive(AlarmReceiver.java:15)
10-27 19:53:01.735: E/AndroidRuntime(28095):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2687)
10-27 19:53:01.735: E/AndroidRuntime(28095):    ... 10 more

Answer 1

首先，不要这样做：

HomeActivity home = new HomeActivity()

您无法手动实例化活动实例。相反，你应该让系统为你做这件事。如果您想start a new activity，请使用Intent。

您可以通过不同的方式回答实际问题，具体取决于您的要求和所需的运行时行为。

例如，如果您只想在应用运行时显示对话框，则可以使用many 'event bus' implementations中的一个，或者只使用接收器设置自己的(local) broadcast manager。

如果您还需要显示对话框，即使您的应用不在前台（如果您决定沿着这条路走下去，也要好好考虑用户体验），您可以利用activity launch modes开始你的HomeActivity。此方法将使您能够优雅地处理后台堆栈上已存在活动记录的场景（以及不存在的场景）。

Answer 2

你不应该这样做：HomeActivity home = new HomeActivity();因为活动是用意图创建的。

您可以这样做：

<强> AlarmReceiver：

@Override
    public void onReceive(Context context, Intent intent) {
    Intent homeActivityIntent = new Intent(context, HomeActivity.class);
    homeActivityIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
    homeActivityIntent.putExtra("value_name", "value_data");
    context.startActivity(homeActivityIntent);
}

<强> HomeActivity：

     @Override
        protected void onNewIntent(Intent intent) {
            super.onNewIntent(intent);
            String someData = intent.getStringExtra("value_name");
            //Maybe check value of someData to decide 
            //weather to open the dialog or not
            this.openDialog();
        }

请帮助，不能从其他类调用android活动方法

2 个答案: