我有一个方法可以设置我想要警报触发的时间。 在这种方法中,我还获得了一个用于取消闹钟的“停止”按钮
if(alarmManager != null){
alarmManager.cancel(pi);
}
我的问题是,当我设置闹钟时,退出应用程序并再次进入以取消闹钟,我得到一个空指针。我猜这是因为当我离开应用程序时 PendingIntent 也会关闭(设置为 null)。
如何防止这种情况发生,以便取消闹钟?
整个方法如下:
@SuppressWarnings("deprecation")
public void setTime(){
Calendar mcurrentTime = Calendar.getInstance();
int hour = mcurrentTime.get(Calendar.HOUR_OF_DAY);
int minute = mcurrentTime.get(Calendar.MINUTE);
TimePickerDialog mTimePicker;
mTimePicker = new TimePickerDialog(MainActivity.this, new TimePickerDialog.OnTimeSetListener()
{
int callCount = 0; //To track number of calls to onTimeSet()
@Override
public void onTimeSet(TimePicker timePicker, int selectedHour, int selectedMinute)
{
if(callCount == 1) // On second call
{
String timeString = "";
timeString = selectedHour + ":" + selectedMinute + ":00";
Log.d("TEST", "Chosen time : "+ timeString);
setAlarm(timePicker, selectedHour, selectedMinute);
}
callCount++; // Incrementing call count.
}
}, hour, minute, true);
mTimePicker.setButton(DialogInterface.BUTTON_POSITIVE, "Set", mTimePicker);
mTimePicker.setButton(DialogInterface.BUTTON_NEGATIVE, "Stop", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if(alarmManager != null){
alarmManager.cancel(pi);
}
}
});
mTimePicker.setTitle(R.string.time);
mTimePicker.show();
}
最佳答案
您可以将用于构造 PendingIntent 的数据保存在 Bundle 中,如 here 所示。
因此,当您再次打开应用程序时,您将能够重建 PendingIntent 并在需要时取消警报。
编辑:首先,您必须重写 onSaveInstanceState
并保存用于创建 PendingIntent 对象的数据,如下所示:
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
// Save the pending intent id
savedInstanceState.putInt(PENDING_INTENT_ID, mPendingIntentId);
// Always call the superclass so it can save the view hierarchy state
super.onSaveInstanceState(savedInstanceState);
}
之后,在您的onCreate
方法中,您将检查savedInstanceState是否不为空。如果不为空,则从savedInstanceState(Bundle)对象中恢复项目,如下所示
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); // Always call the superclass first
// Check whether we're recreating a previously destroyed instance
if (savedInstanceState != null) {
// Restore value of members from saved state
mPendingIntentId = savedInstanceState.getInt(PENDING_INTENT_ID);
} else {
// Probably initialize members with default values for a new instance
mPendingIntentId = YOUR_DEFAULT_INT_VALUE;
}
mPendingIntent = PendingIntent.getBroadcast(this, mPendingIntentId, YOUR_INTENT, PendindIntent.FLAG_UPDATE_CURRENT);
}
每次您进入应用程序时,都会重新创建 PendingIntent,因此您将能够取消在上一步中触发的同一警报。
编辑2:您的情况的另一种方法是,由于您只有一个警报,并且它的ID始终相同(应该用于PendingIntent的requestId),所以您可以在需要时简单地重新创建PendingIntent添加或取消闹钟。像下面这样的方法可以帮助您。
private PendingIntent getPendingIntent(Context context){
return PendingIntent.getBroadcast(context, 0, new Intent(context, YourBroadcastReceiver.class), PendingIntent.FLAG_CANCEL_CURRENT);
}
关于java - 取消 AlarmManager,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/26525731/