Question

我正在尝试在我的Android应用中使用DatePicker。当我将它添加到我的布局时，我收到此消息：

The following classes could not be instantiated:
- android.widget.DatePicker (Open Class, Show Error Log)
See the Error Log (Window > Show View) for more details.

所以我查看了错误日志，这就是我所看到的：

android.widget.DatePicker failed to instantiate.
java.lang.NoClassDefFoundError: java/nio/charset/Charsets
    at android.net.Uri.decode(Uri.java:1927)
    at android.net.Uri$AbstractPart.getDecoded(Uri.java:1957)
    at android.net.Uri$StringUri.getAuthority(Uri.java:579)
    at android.provider.Settings$NameValueCache.getString(Settings.java:727)
    at android.provider.Settings$System.getString(Settings.java:846)
    at android.text.format.DateFormat.getDateFormatString(DateFormat.java:393)
    at android.text.format.DateFormat.getDateFormatOrder(DateFormat.java:364)
    at android.widget.DatePicker.reorderSpinners(DatePicker.java:511)
    at android.widget.DatePicker.<init>(DatePicker.java:280)
    at android.widget.DatePicker.<init>(DatePicker.java:145)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.instantiateClass(ProjectCallback.java:402)
    at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.loadView(ProjectCallback.java:166)
    at android.view.BridgeInflater.loadCustomView(BridgeInflater.java:207)
    at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:135)
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:746)
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:718)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:372)
    at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:321)
    at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:331)
    at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:325)
    at com.android.ide.eclipse.adt.internal.editors.layout.gle2.RenderService.createRenderSession(RenderService.java:372)
    at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.renderWithBridge(GraphicalEditorPart.java:1640)
    at [SNIPPED FOR LENGTH; SEE REVISION HISTORY FOR FULL TRACE -ed]

为什么会这样？

Answer 1

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/btnChangeDate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Change Date" />

    <TextView
        android:id="@+id/lblDate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Current Date (M-D-YYYY): "
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/tvDate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <DatePicker
        android:id="@+id/dpResult"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
 </LinearLayout>

import java.util.Calendar;
import android.app.Activity;
import android.app.DatePickerDialog;
import android.app.Dialog;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.TextView;

public class MyAndroidAppActivity extends Activity {

    private TextView tvDisplayDate;
    private DatePicker dpResult;
    private Button btnChangeDate;

    private int year;
    private int month;
    private int day;

    static final int DATE_DIALOG_ID = 999;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        setCurrentDateOnView();
        addListenerOnButton();

    }

    // display current date
    public void setCurrentDateOnView() {

        tvDisplayDate = (TextView) findViewById(R.id.tvDate);
        dpResult = (DatePicker) findViewById(R.id.dpResult);

        final Calendar c = Calendar.getInstance();
        year = c.get(Calendar.YEAR);
        month = c.get(Calendar.MONTH);
        day = c.get(Calendar.DAY_OF_MONTH);

        // set current date into textview
        tvDisplayDate.setText(new StringBuilder()
            // Month is 0 based, just add 1
            .append(month + 1).append("-").append(day).append("-")
            .append(year).append(" "));

        // set current date into datepicker
        dpResult.init(year, month, day, null);

    }

    public void addListenerOnButton() {

        btnChangeDate = (Button) findViewById(R.id.btnChangeDate);

        btnChangeDate.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                showDialog(DATE_DIALOG_ID);

            }

        });

    }

    @Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case DATE_DIALOG_ID:
           // set date picker as current date
           return new DatePickerDialog(this, datePickerListener, 
                         year, month,day);
        }
        return null;
    }

    private DatePickerDialog.OnDateSetListener datePickerListener 
                = new DatePickerDialog.OnDateSetListener() {

        // when dialog box is closed, below method will be called.
        public void onDateSet(DatePicker view, int selectedYear,
                int selectedMonth, int selectedDay) {
            year = selectedYear;
            month = selectedMonth;
            day = selectedDay;

            // set selected date into textview
            tvDisplayDate.setText(new StringBuilder().append(month + 1)
               .append("-").append(day).append("-").append(year)
               .append(" "));

            // set selected date into datepicker also
            dpResult.init(year, month, day, null);

        }
    };

}

阅读此代码可能对您有所帮助

DatePicker不起作用

1 个答案: