从 DatePicker 更新 TextView

Question

我正在尝试从 Datepicker 中更新 TextView，但是我收到了错误

“不能从静态上下文引用非静态方法（updateDateTextView(long)）”

这是我的 DatePickerFragment.java

public class DatePickerFragment extends DialogFragment
        implements DatePickerDialog.OnDateSetListener {

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Use the current date as the default date in the picker
        final Calendar c = Calendar.getInstance();
        int year = c.get(Calendar.YEAR);
        int month = c.get(Calendar.MONTH);
        int day = c.get(Calendar.DAY_OF_MONTH);

        // Create a new instance of DatePickerDialog and return it
        return new DatePickerDialog(getActivity(), this, year, month, day);
    }

    public void onDateSet(DatePicker view, int year, int month, int day) {
        Calendar calendar = new GregorianCalendar(year, month, day);
        long timestamp = TimeUnit.MILLISECONDS.toSeconds(calendar.getTimeInMillis());
        AddItem.updateDateTextView(timestamp);
    }
}

这是我在 AddItem.java 中的函数，它是一个 Activity。

      public  class AddItem extends AppCompatActivity {

    Context ctx = this;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_item);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

    }
    public void showDatePickerDialog(View v) {
        DialogFragment newFragment = new DatePickerFragment();
        newFragment.show(getFragmentManager(), "datePicker");
    }

    public void updateDateTextView(long timestamp){
        TextView textViewToChange = (TextView) findViewById(R.id.openDate);
        Calendar cal = Calendar.getInstance(Locale.ENGLISH);
        cal.setTimeInMillis(timestamp);
        String date = DateFormat.format("dd-MM-yyyy", cal).toString();
        textViewToChange.setText(date);
    }

}

Answer 1

正如他们所说，您不能像静态方法那样调用非静态方法。试试这个：

在您的 Activity 中实现 DatePickerDialog.OnDateSetListener 和逻辑：

public class AddItem extends AppCompatActivity implements DatePickerDialog.OnDateSetListener {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    showDatePickerDialog();
}

public void showDatePickerDialog() {
    DatePickerFragment newFragment = new DatePickerFragment();
    newFragment.init(this, this);
    newFragment.show(getSupportFragmentManager(), "date_picker");
}

public void updateDateTextView(long timestamp){
    TextView textViewToChange = (TextView) findViewById(R.id.openDate);
    Calendar cal = Calendar.getInstance(Locale.ENGLISH);
    cal.setTimeInMillis(timestamp);
    String date = DateFormat.format("dd-MM-yyyy", cal).toString();
    textViewToChange.setText(date);
}

@Override
public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {

    Calendar calendar = new GregorianCalendar(year, monthOfYear, dayOfMonth);
        long timestamp = TimeUnit.MILLISECONDS.toSeconds(calendar.getTimeInMillis());

        updateDateTextView(timestamp);
}

并用监听器初始化 DatePicker，类应该是这样的：

public static class DatePickerFragment extends DialogFragment {

    DatePickerDialog.OnDateSetListener listener;
    Context context;

    public void init(Context context, DatePickerDialog.OnDateSetListener listener) {
        this.listener = listener;
        this.context = context;
    }

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Use the current date as the default date in the picker
        final Calendar c = Calendar.getInstance();
        int year = c.get(Calendar.YEAR);
        int month = c.get(Calendar.MONTH);
        int day = c.get(Calendar.DAY_OF_MONTH);

        // Create a new instance of DatePickerDialog and return it
        return new DatePickerDialog(context, listener, year, month, day);
    }

}

我试过了，效果很好。

Answer 2

非静态方法不能与静态类一起使用 尝试改变

public void updateDateTextView(long timestamp){ ..... }

到

public static void updateDateTextView(long timestamp){
...}

Answer 3

你正在这样做：

public void onDateSet(DatePicker view, int year, int month, int day) {
        Calendar calendar = new GregorianCalendar(year, month, day);
        long timestamp = TimeUnit.MILLISECONDS.toSeconds(calendar.getTimeInMillis());
        AddItem.updateDateTextView(timestamp); ///Here is the error
    }

错误是 AddITem.updateDateTextView 错误。 updateDateTextView 方法不是静态的。

您需要使用 Intent 启动该 Activity，并且在生命周期中的某处调用方法 updateDateTextView

或

修改方法并使其成为静态（但这不是开发人员的好主意）

public static void onDateSet(DatePicker view, int year, int month, int day)

Answer 4

也可以在 DatePickerFragment 类中定义一个interface，如下面的代码所示。

public class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {

DateChooserListenerHandler dateChooserListenerHandler;
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    // Use the current date as the default date in the picker
    final Calendar c = Calendar.getInstance();
    int year = c.get(Calendar.YEAR);
    int month = c.get(Calendar.MONTH);
    int day = c.get(Calendar.DAY_OF_MONTH);

    // Create a new instance of DatePickerDialog and return it
    return new DatePickerDialog(getActivity(), this, year, month, day);
}
@Override
public void onDateSet(DatePicker datePicker, int year, int month, int day) {
    Calendar calendar = new GregorianCalendar(year, month, day);
    long timestamp = TimeUnit.MILLISECONDS.toSeconds(calendar.getTimeInMillis());
    //Note this is where the updateTextView method in the interface is invoked from
    ((DateChooserListenerHandler) getActivity()).updateTextView(timestamp);
}

//Define an interface with a method that takes long, it will be overridden by classes that implement the interface
public interface DateChooserListenerHandler{

    public void updateTextView(long s);
}

}

然后 AddItem 活动类可以实现如下代码中的接口。

public class AddItem extends AppCompatActivity implements DatePickerFragment.DateChooserListenerHandler {


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

}

public void showDatePickerDialog(View v) {
    DialogFragment newFragment = new DatePickerFragment();
    newFragment.show(getSupportFragmentManager(), "timePicker");
}

//The overridden method from the interface defined in DatePickerFragment class
@Override
public void updateTextView(long s) {
    updateDateTextView(s);
}

public void updateDateTextView(long timestamp){
    TextView textViewToChange = (TextView) findViewById(R.id.textView);
    Calendar cal = Calendar.getInstance(Locale.ENGLISH);
    cal.setTimeInMillis(timestamp);
    String date = DateFormat.format("dd-MM-yyyy", cal).toString();
    textViewToChange.setText(date);
}

}

这对我来说很好，但是我没有检查它对应用程序的性能影响，但我发现它更容易。 如果您只想直接从 DatePickerFragment 更新 TextView，那么您可以像下面这样进行。

 @Override
public void onDateSet(DatePicker datePicker, int year, int month, int day) {
    Calendar calendar = new GregorianCalendar(year, month, day);
    long timestamp = TimeUnit.MILLISECONDS.toSeconds(calendar.getTimeInMillis());
    TextView textView = (TextView) getActivity().findViewById(R.id.textView);
    textView.setText(timestamp + "");
}