时间选择器小部件 - “id 无法解析或不是字段”

Question

我收到以下几行错误：

mTimeDisplay = (TextView) findViewById(R.id.timeDisplay);
mPickTime = (Button) findViewById(R.id.pickTime);

虽然在这个阶段我只是复制粘贴教程中的内容，只是为了感受一下。那么我哪里错了？

这是整个 .java 文件：

package com.example.hellotimepicker;

import java.util.Calendar;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class HelloTimePicker extends Activity {
    /** Called when the activity is first created. */

    private TextView mTimeDisplay;
    private Button mPickTime;

    private int mHour;
    private int mMinute;

    static final int TIME_DIALOG_ID = 0;

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

        // capture our View elements
        mTimeDisplay = (TextView) findViewById(R.id.timeDisplay);
        mPickTime = (Button) findViewById(R.id.pickTime);

        // add a click listener to the button
        mPickTime.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                showDialog(TIME_DIALOG_ID);
            }
        });

        // get the current time
        final Calendar c = Calendar.getInstance();
        mHour = c.get(Calendar.HOUR_OF_DAY);
        mMinute = c.get(Calendar.MINUTE);

        // display the current date
        updateDisplay();

    }

 // updates the time we display in the TextView
    private void updateDisplay() {
        mTimeDisplay.setText(
            new StringBuilder()
                    .append(pad(mHour)).append(":")
                    .append(pad(mMinute)));
    }

    private static String pad(int c) {
        if (c >= 10)
            return String.valueOf(c);
        else
            return "0" + String.valueOf(c);
    }
}

Answer 1

听起来您错过了从教程中复制布局（xml 代码）

Answer 2

只是想分享我对原始教程版本的经验，因为这可能有用。之前我使用过：

import android.R;

但是 main 无法在该行解析：

setContentView(R.layout.main);

所以我将 "import android.R;" 更改为：

import com.example.hellodatepicker.R; //to match with the package name

并发现它运行良好。