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我在與通知從/發送到片段未來問題會片段。我會盡可能清楚地解釋我的情況以顯示問題。Android的錯誤從通知
我有一個活動，MyWorkout.java，這一活動具有可擴展列表視圖。可展開列表視圖上的所有項目都會將用戶發送到第二個活動WorkoutDaysActivity。他們都發送一個單獨的額外意圖，所以我知道用戶點擊了哪個項目。在WorkoutDaysActivity.java中，創建3個片段，星期一，星期三和星期五。我爲每個活動單獨分班。這些類具有回收器視圖和計時器。我擁有它，當定時器結束時，用戶會收到通知。這是有效的，但是當我嘗試從通知中將用戶發送到WorkoutDaysActivity時，它會崩潰並顯示下面的錯誤。
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.hashCode()' on a null object reference
at com.bestworkouts.sheikoworkout.WorkoutDaysActivity.addPages(WorkoutDaysActivity.java:45)
at com.bestworkouts.sheikoworkout.WorkoutDaysActivity.onCreate(WorkoutDaysActivity.java:29)
，它給我發過該線是它試圖爲基於從MyWorkout.java傳遞的意圖標題（以下switch語句）。我猜這是因爲其目的不通過，因爲他們獲得這一類從通知而不是從MyWorkout.java，因此字符串標題爲空。我的問題是我不知道如何解決這個問題。通知工作正常，如果我把它發送到MyWorkout.java，但我更願意把它送回來到定時器如果可能的設置。
public class WorkoutDaysActivity extends BaseActivity{
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.workout_days);
mToolBar = activateToolbar();
setUpNavigationDrawer();
ViewPager vp = (ViewPager) findViewById(R.id.view_pager);
this.addPages(vp);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.setupWithViewPager(vp);
tabLayout.setOnTabSelectedListener(listener(vp));
}
//ADD ALL PAGES
private void addPages(ViewPager pager) {
MyFragPagerAdapter adapter = new MyFragPagerAdapter(getSupportFragmentManager());
Intent intent = getIntent();
String workout = intent.getStringExtra("workout");
Bundle args = new Bundle();
args.putString("workout", workout);
String title = args.getString("workout");
switch(title) {
case "w29w1" : {
getSupportActionBar().setTitle("Workout 29 Week 1");
break;
}
case "w29w2" : {
getSupportActionBar().setTitle("Workout 29 Week 2");
break;
}
MondayFragment mondayFragment = new MondayFragment();
mondayFragment.setArguments(args);
adapter.addPage(mondayFragment);
WedFragment wedFragment = new WedFragment();
wedFragment.setArguments(args);
adapter.addPage(wedFragment);
FridayFragment fridayFragment = new FridayFragment();
fridayFragment.setArguments(args);
adapter.addPage(fridayFragment);
pager.setAdapter(adapter);
}
這就是定時器（MondayFragment.java）：
private Button btnStart;
private Button btnStop;
private Button btnReset;
private CountDownTimer mCountDownTimer;
private TextView txtViewRest;
private void start() {
mCountDownTimer = new CountDownTimer(5000, 1000) {
@Override
public void onTick(long millisUntilFinished) {
txtViewRest.setText("Rest Remaining: " + millisUntilFinished/1000 + " seconds.");
}
@Override
public void onFinish() {
txtViewRest.setText("Done!");
showNotification();
}
}.start();
}
public void cancel() {
if (mCountDownTimer != null) {
mCountDownTimer.cancel();
txtViewRest.setText("Rest Remaining: 5 seconds");
} else return;
}
public void reset() {
if (mCountDownTimer != null) {
mCountDownTimer.cancel();
txtViewRest.setText("Rest Remaining: 5 Seconds");
} else return;
}
public void showNotification() {
NotificationCompat.Builder builder = new NotificationCompat.Builder(getContext());
builder.setSmallIcon(R.drawable.sheikoicon);
builder.setContentTitle("Sheiko Rest Timer");
builder.setContentText("Rest timer is up, start your set!");
builder.setDefaults(Notification.DEFAULT_SOUND|Notification.DEFAULT_VIBRATE);
builder.setAutoCancel(true);
Intent intent = new Intent(getActivity(), WorkoutDaysActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
TaskStackBuilder stackBuilder = TaskStackBuilder.create(getContext());
stackBuilder.addParentStack(WorkoutDaysActivity.class);
stackBuilder.addNextIntent(intent);
PendingIntent pendingIntent = stackBuilder.getPendingIntent(0, PendingIntent.FLAG_NO_CREATE);
builder.setContentIntent(pendingIntent);
NotificationManager NM = (NotificationManager) getActivity().getSystemService(Context.NOTIFICATION_SERVICE);
NM.notify(0, builder.build());
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
SharedPreferences pref = this.getActivity().getSharedPreferences("MyPref", 0);
View view = inflater.inflate(R.layout.monday_fragment, null);
txtViewRest = (TextView) view.findViewById(R.id.txtViewRest);
btnStart = (Button) view.findViewById(R.id.btnStart);
btnStop = (Button) view.findViewById(R.id.btnStop);
btnReset = (Button) view.findViewById(R.id.btnReset);
btnStart.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
start();
}
});
btnStop.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
cancel();
}
});
btnReset.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
reset();
}
});
任何及所有的幫助感激！
addPages方法中的第45行，那裏的東西是null。 – AndroidRuntimeException
是的，我認爲這是因爲它是從上一課獲得意圖。是否有，我可以保存片段的狀態或什麼？所以如果我把它發送給我的片段與以前有相同的狀態，我得到了通知？ – LBJ33
當然，檢查這個帖子http://stackoverflow.com/questions/22505327/android-save-restore-fragment-state – AndroidRuntimeException