从对话框片段中获取变量以返回到调用它的活动

Question

在我正在编写的一个安卓应用程序中，我正在使用TimeDurationPicker进行对话。我希望用户输入计时器的持续时间，并将该持续时间传递回调用它的活动。我知道已经有关于这个问题的答案了，但我还没能让任何东西正常工作。

下面是活动：

public class train extends AppCompatActivity {
    public Integer customTimerlength = null;
    public Integer timerDurationSeconds = 180;  // 3 minutes is a good default value
    public boolean timerIsPaused;
    public long millisLeftOnTimer;
    Button startBreakTimerButton;
    Button stopBreakTimerButton;
    Button pauseBreakTimerButton;
    TextView breakTimerOutput;
    CountDownTimer countdowntimer;
    private CountDownTimer mCountDownTimer;

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

        startBreakTimerButton = (Button) findViewById(R.id.startBreakTimer);
        stopBreakTimerButton = (Button) findViewById(R.id.stopBreakButton);
        pauseBreakTimerButton = (Button) findViewById(R.id.pauseBreakButton);
        breakTimerOutput = (TextView) findViewById(R.id.breakTimerOutput);

        // Break timer long-click set time
        breakTimerOutput.setOnLongClickListener(new OnLongClickListener() {

            @Override
            public boolean onLongClick(View v) {
                //customTimerlength = timerLengthInputAlert();

                new RestDurationPicker().show(getFragmentManager(), "Session break length");

下面是这段代码：

import android.widget.Toast;
import mobi.upod.timedurationpicker.TimeDurationPicker;
import mobi.upod.timedurationpicker.TimeDurationPickerDialogFragment;

public class RestDurationPicker extends TimeDurationPickerDialogFragment {

    @Override
    protected long getInitialDuration() {
        return 0;  // Default to empty
    }

    @Override
    protected int setTimeUnits() {
        return TimeDurationPicker.MM_SS;
    }

    @Override
    public void onDurationSet(TimeDurationPicker view, long duration) {
        Toast.makeText(getContext(), "New break duration set", Toast.LENGTH_LONG).show();
    }
}

我在这里找到了相当多的关于意图和接口的答案，但我无法让任何东西工作，我感到不知所措。这是我第一次尝试Android应用程序，所以我不知道还能做什么。

我真的很感谢你的提前帮助！

Answer 1

想明白了！

我将这个添加到我的活动中：

// Break timer long-click set time
@Override
public void onDurationSet(long duration) {
    Integer i = (int) (long) duration;  // get integer i from duration (long)
    customTimerlength = i / 1000; // convert millis to seconds

    // Set the timer duration in seconds
    timerDurationSeconds = customTimerlength;

    // Assign the new custom timer duration to the timerduration variable
    breakTimerOutput.setText(Integer.toString(timerDurationSeconds));
    Log.d("NewTimer", "New Timer Duration: " + timerDurationSeconds);
}

public interface DurationListener {
    void onDurationSet(long duration);
}

片段现在根据需要将持续时间传递给活动。

Answer 2

为了让您的活动从DialogFragment接收持续时间，您需要创建一个接口。下面是一个例子

public interface DurationListener {
    void onDurationSet(long duration);
}

然后，您的活动应该实现此接口。换句话说，该活动必须通过实现onDurationSet()方法来遵循接口约定的条款。

public class TrainActivity extends AppCompatActivity implements DurationListener {
    //skipping most of your code

    @Override
    public void onDurationSet(long duration) {
        //Do something with the duration
    }

}

现在，在DialogFragment中，您需要更改构造函数以接受DurationListener，并且当用户更改持续时间时，需要在侦听器上调用onDurationSet()。

public class RestDurationPicker extends TimeDurationPickerDialogFragment {
    private final DurationListener mListener;

    public RestDurationPicker() {}

    //The modified constructor, which accepts a listener as a parameter
    public RestDurationPicker(DurationListener listener) {
        mListener = listener;
    }

    //Most of your code goes here

    @Override
    public void onDurationSet(TimeDurationPicker view, long duration) {
        //When the duration is set by the user, notify the listener
        listener.onDurationSet(duration);
    }
}

现在，当您创建DialogFragment时，只需将活动传递给片段，就完成了！

//This code is in your onCreate method in your activity
breakTimerOutput.setOnLongClickListener(new OnLongClickListener() {

    @Override
    public boolean onLongClick(View v) {
        //customTimerlength = timerLengthInputAlert();

        new RestDurationPicker(this).show(getFragmentManager(), "Session break length");
    }
});

附注:您应该确保您的代码遵循Java和Android编码指南，即对类和方法使用正确的命名约定，并保持类字段为私有或受保护，除非您有理由将其设置为公共字段。此链接可帮助您完成此操作：https://source.android.com/source/code-style.html