Android 错误从通知转到片段
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【中文标题】Android 错误从通知转到片段【英文标题】：Android Error going to fragments from notification 【发布时间】：2016-12-30 16:36:39 【问题描述】：我遇到来自/发送到片段的通知的问题。我将尝试尽可能清楚地解释我的方案以显示问题。
我有一个活动，MyWorkout.java，这个活动有一个可展开的列表视图。可展开列表视图上的所有项目将用户发送到第二个活动 WorkoutDaysActivity。他们都发送一个单独的额外意图，所以我知道用户点击了哪个项目。在 WorkoutDaysActivity.java 中，创建了 3 个片段，即星期一、星期三和星期五。每个活动我都有单独的课程。这些类有一个回收器视图和一个计时器。我有它，所以当计时器结束时，用户会收到通知。这可行，但是当我尝试从通知中将用户发送到 WorkoutDaysActivity 时，它会因以下错误而崩溃。
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)
它发送给我的那行也是它尝试根据从 MyWorkout.java 传递的意图设置标题（下面的 switch 语句）的地方。我猜这是因为当他们从通知而不是从 MyWorkout.java 到达此类时，意图没有传递，因此字符串标题为空。我的问题是我不知道如何解决这个问题。如果我将通知发送到 MyWorkout.java，通知工作正常，但如果可能，我更愿意将其发送回设置计时器的位置。
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);
这是计时器所在的位置（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();
);
非常感谢任何和所有帮助！
【问题讨论】：
addPages 方法中的第 45 行，那里有些内容为空。 是的，我认为这是因为假设它是从上一课获得意图的。无论如何我可以保存片段的状态或其他东西吗？因此，如果我将其发送到我的片段是否与收到通知之前的状态相同？ 当然，查看这个帖子***.com/questions/22505327/… 谢谢！我不确定这是否是我的问题.. 我认为这与我的标志或 showNotification 方法中的某些东西有关 "WorkoutDaysActivity.java:45" 这意味着错误发生在 WorkoutDaysActivity.java 的第 45 行。这是哪条线？ 【参考方案1】：我设法解决了这个问题，我会在这里发布解决方案，以防将来有人遇到同样的问题。
这实际上是一个非常简单的修复，我所要做的就是在通知代码中添加额外的意图。
所以我从 MyWorkout.java 将这个意图传递给了 WorkoutDaysActivity：
Intent intent = new Intent(getApplicationContext(), WorkoutDaysActivity.class);
intent.putExtra("workout", "w29w1");
startActivity(intent);
在锻炼日活动中，我有这个意图，并将它作为参数传递给所有三个片段，如下所示：
Intent intent = getIntent();
String workout = intent.getStringExtra("workout");
Bundle args = new Bundle();
args.putString("workout", workout);
MondayFragment mondayFragment = new MondayFragment();
mondayFragment.setArguments(args);
adapter.addPage(mondayFragment);
WedFragment wedFragment = new WedFragment();
wedFragment.setArguments(args);
adapter.addPage(wedFragment);
然后在我发出通知的每个片段中，我必须添加 intent.putExtra
public void showNotification()
NotificationCompat.Builder builder = new NotificationCompat.Builder(getContext());
builder.setSmallIcon(R.drawable.sheikoicon);
builder.setContentTitle("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.putExtra("workout", workout3);
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_UPDATE_CURRENT);
builder.setContentIntent(pendingIntent);
NotificationManager NM = (NotificationManager) getActivity().getSystemService(Context.NOTIFICATION_SERVICE);
NM.notify(0, builder.build());
锻炼3在哪里：
args = getArguments();
workout3 = args.getString("workout");
【讨论】：
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