当应用程序处于 onStop() 状态时如何启动对话框？

Question

我正在创建一个使用线程的计时器应用程序。当我使用主页按钮退出应用程序时，计时器运行正常。通常，当时间到了时，会启动一个对话框，询问用户一些输入。如果应用程序处于其 onResume() 状态，这完全可以正常工作，但是当应用程序处于其 onStop() 状态时，对话框将不会启动并引发错误。

java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState

我怎样才能做到这一点，当时间到了并且应用程序不在前台时，对话框仍然会启动。我最初的想法是节省捆绑包中剩余的时间，但剩余时间会随着每个滴答声而变化。然后我考虑在包 mTimeRunning 中存储一个布尔值。然而，当时间到了，这个值也必须改变。所以现在我正在画一个空白。我该怎么做才能在应用不在前台时启动对话框？

TimerActivity.java

public class TimerActivity extends AppCompatActivity implements TimeDialogFragment.sendMinutes, 
TimeFinishDialogFragment.sendResponse, BreakFinishDialogFragment.userResponse {


// Variable to log activity state
private static final String TAG = "TimerActivity";
private static final boolean DEBUG = true;
// ^^ Variable used to log acitivty state


private Handler mHandler;
private Runnable mRunnable;

//private static final long START_TIME_MILLISECONDS = 600000;
// Below start time is for development purposes only
private static long mStartTime = 10000;
private long mTimeRemaining = mStartTime;

private boolean mTimeRunning;

private boolean mBreakTime = false;

private ProgressBar mTimeBar;
private TextView mTime;
private Button mStartPause;

private Button mSetTime;

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

    if(DEBUG) Log.d(TAG, "+ onCreate() +");

    mHandler = new Handler();


    mTimeBar = findViewById(R.id.time_bar);
    mTime = findViewById(R.id.text_view_time);
    mStartPause = findViewById(R.id.button_start_pause);

    mSetTime = findViewById(R.id.button_set_time);
    updateCountDownText();
    mTimeBar.setMax((int) mTimeRemaining);


    mSetTime.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //FragmentManager manager = getSupportFragmentManager();
            DialogFragment setTime = new TimeDialogFragment();
            setTime.show(getFragmentManager(),"SET_TIME_DIALOG");
        }
    });


    mStartPause.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(mTimeRunning){
                //pauseTimer();
                mTimeRunning = false;
                mStartPause.setText("Start");
                mHandler.removeCallbacks(mRunnable);
            }else{
                //startTimer();
                timer();
            }
        }
    });
}

// Using a handler + anon runnable

private void timer(){
    mRunnable = new Runnable() {
        @Override
        public void run() {
            mTimeRunning = true;
            mStartPause.setText("Pause");
            mTimeRemaining = mTimeRemaining - 1000;
            updateCountDownText();
            mTimeBar.incrementProgressBy(1000);
            if(mTimeRemaining > 0) {
                mHandler.postDelayed(this, 1000);
            }else{
                // if breaktime is false
                if(!mBreakTime) {

                    DialogFragment dialog = new TimeFinishDialogFragment();
                    dialog.show(getFragmentManager(),"TIME_FINISH_DIALOG");

                    mTimeRunning = false;
                }else{
                    // launch break time up dialog.
                    mBreakTime = false;

                    DialogFragment dialog = new BreakFinishDialogFragment();
                    dialog.show(getFragmentManager(), "BREAK_FINSIH_DIALOG");

                }
            }
        }
    };
    mHandler.postDelayed(mRunnable,1000);
}


public void updateCountDownText(){
    int min = (int) (mTimeRemaining / 1000) / 60;
    int sec = (int) (mTimeRemaining / 1000) % 60;

    String formattedString = String.format(Locale.getDefault(), "%02d:%02d", min, sec);

    mTime.setText(formattedString);
}

public void setCountDownText(long time){
    int min = (int) (time / 1000) / 60;
    int sec = (int) (time / 1000) % 60;

    String formattedString = String.format(Locale.getDefault(), "%02d:%02d", min, sec);

    mTime.setText(formattedString);
}

@Override
public void userTime(int minutes) {
    TimerActivity.mStartTime = (minutes * 60) * 1000;
    mTimeRemaining = TimerActivity.mStartTime;
    mTimeBar.setMax((int) mTimeRemaining);

    setCountDownText(mTimeRemaining);
}

@Override
public void sendResponse(int val) {
    if(val == -1){
        mTimeRemaining = TimerActivity.mStartTime;
        mTimeBar.setMax((int) mTimeRemaining);
        updateCountDownText();
        mTimeBar.setProgress(0);
        mStartPause.setText("Start");
    }else if(val == 1) {
        mBreakTime = true;
        mTimeRemaining = 15000;
        mTimeBar.setMax((int) mTimeRemaining);
        setCountDownText(mTimeRemaining);
        mTimeBar.setProgress(0);
        mStartPause.setVisibility(View.INVISIBLE);
        timer();
    }else {
        mTimeRemaining = TimerActivity.mStartTime;
        mTimeBar.setMax((int) mTimeRemaining);
        updateCountDownText();
        mTimeBar.setProgress(0);
        timer();
    }
}

@Override
public void userResponse(int val) {
    if(val < 0) {
        // user clicked cance
        mTimeRemaining = TimerActivity.mStartTime;
        mTimeBar.setMax((int) mTimeRemaining);
        updateCountDownText();
        mTimeBar.setProgress(0);
        mStartPause.setText("Start");
    }else {
        mTimeRemaining = TimerActivity.mStartTime;
        mTimeBar.setMax((int) mTimeRemaining);
        updateCountDownText();
        mTimeBar.setProgress(0);
        timer();
    }

    mStartPause.setVisibility(View.VISIBLE);
}

TimeFinishedDialog.java

public class TimeFinishDialogFragment extends DialogFragment implements View.OnClickListener{

private Button mCancel;
private Button mSkip;
private Button mStartBreak;

private sendResponse mResponse;
interface sendResponse{
    void sendResponse(int val);
}

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    //return super.onCreateDialog(savedInstanceState);
    View view = LayoutInflater.from(getActivity()).inflate(R.layout.time_finish_dialog_fragment, null, false);

    mCancel = view.findViewById(R.id.button_cancel);
    mSkip = view.findViewById(R.id.button_skip);
    mStartBreak = view.findViewById(R.id.button_start_break);

    mCancel.setOnClickListener(this);
    mSkip.setOnClickListener(this);
    mStartBreak.setOnClickListener(this);

    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    builder.setView(view)
           .setTitle("Start Break?");

    AlertDialog dialog = builder.create();
    dialog.setContentView(view);
    return dialog;
}

@Override
public void onClick(View view) {
    switch(view.getId()){
        case R.id.button_cancel:
            mResponse.sendResponse(-1);
            getDialog().dismiss();
            break;
        case R.id.button_skip:
            mResponse.sendResponse(0);
            getDialog().dismiss();
            break;
        case R.id.button_start_break:
            mResponse.sendResponse(1);
            getDialog().dismiss();
            break;
        default:
            break;
    }
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    try{
        mResponse = (sendResponse) getActivity();
    }catch (ClassCastException e){
        System.out.println("Error: " + e);
    }
}
}

Answer 1

当时间到并且应用不在前台时，对话框仍会启动

你不应该这样做，因为这会打断用户做他们当时可能正在做的其他工作，这可能会让人恼火。

当应用不在前台时，我该怎么做才能启动对话框？

您可以仅在用户正在积极使用您的应用程序时显示对话框，也可以在用户未使用应用程序时退回以显示通知。

如果你非常想显示一个对话框，你可以试试dialog themed activity