[英]How to call the method in Main_Activity Class from Helper class?
[英]how to call a method of a main_activity from a normal class in android
嗨,我在android后台进程中使用此帖子android上的后台进程计时器
我在主要活动中的计时器代码是
int repeatTime = 5;
AlarmManager processTimer = (AlarmManager)getSystemService(ALARM_SERVICE);
Intent intent = new Intent(this, processTimerReceiver.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
processTimer.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(),repeatTime*1000, pendingIntent);
我在processTimerReceiver类中的代码是:
public class processTimerReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
MainActivity m = new MainActivity();
m.get_start_info();
}
}
我想在主要活动中调用方法get_start_info(),但应用崩溃
我的主要活动是:
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
setContentView(R.layout.activity_main);
int repeatTime = 5;
AlarmManager processTimer = (AlarmManager)getSystemService(ALARM_SERVICE);
Intent intent = new Intent(this, processTimerReceiver.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
processTimer.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(),repeatTime*1000, pendingIntent);
get_start_info();
}
public void get_start_info() {
JsonArrayRequest movieReq = new JsonArrayRequest("www.example.com",
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
try {
JSONObject obj = response.getJSONObject(0);
// any
sendNotification();
//any
} catch (Exception e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
AppController.getInstance().addToRequestQueue(movieReq);
}
public void sendNotification() {
NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
builder.setSmallIcon(android.R.drawable.ic_dialog_email);
Uri soundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
Intent intent = new Intent(MainActivity.this, azegar_mail_list.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, 0);
//mp.start();
builder.setContentIntent(pendingIntent);
builder.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher));
builder.setContentTitle("آزگار");
builder.setContentText("نامه جدید برای شما ارسال شده است");
builder.setAutoCancel(true);
builder.setSound(soundUri);
NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
// Will display the notification in the notification bar
notificationManager.notify(1, builder.build());
}
}
我的错误是:
E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start receiver com.azegar.www.azegar.processTimerReceiver: java.lang.NullPointerException
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2539)
at android.app.ActivityThread.access$1500(ActivityThread.java:167)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1432)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:153)
at android.app.ActivityThread.main(ActivityThread.java:5341)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:929)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.content.ContextWrapper.getResources(ContextWrapper.java:89)
at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:78)
at android.support.v7.app.AppCompatActivity.getResources(AppCompatActivity.java:551)
at android.content.Context.getString(Context.java:327)
at com.azegar.www.azegar.MainActivity.get_start_info(MainActivity.java:438)
at com.azegar.www.azegar.processTimerReceiver.onReceive(processTimerReceiver.java:12)
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2532)
at android.app.ActivityThread.access$1500(ActivityThread.java:167)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1432)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:153)
at android.app.ActivityThread.main(ActivityThread.java:5341)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:929)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
at dalvik.system.NativeStart.main(Native Method)
首先,如果要在MainActivity之外调用get_start_info()
,则将get_start_info()
和sendNotification
移出MainActivity。
之所以得到NullPointerException
是因为尝试使用MainActivity
的上下文在sendNotification
内构建通知,而该上下文为null,因为您正在使用new
关键字实例化MainActivity
(不应使用new
关键字实例化新活动)。 而是将BroadcastReceiver
的上下文作为参数传递给sendNotification
并使用它来构建通知。
使用Context
部分代码:
NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
Intent intent = new Intent(MainActivity.this, azegar_mail_list.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, 0);
在这里,不要使用this
,而应该使用作为参数传递的Context
。
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