使用Eclipse，我得到一个错误“变量”，该错误无法解决或不是字段，我不确定为什么

Question

It occurs in the MainActivity.java portion and there are no errors in any other folder. I have tried everything I could find and saw that it is a bug in Eclipse but sometimes it is the fault of the programmer. I'm not sure which this case is for me. "Variable" in this case is for any line with R.id."variable".

package com.example.tipcalculator1;

import java.text.NumberFormat;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.TextView.OnEditorActionListener;
import android.app.Activity;

public class MainActivity extends ActionBarActivity implements
    OnEditorActionListener, OnClickListener {
// define instance variables for the widgets
EditText billAmountEditText;
TextView percentTextView;
Button percentUpButton;
Button percentDownButton;
TextView tipTextView;
TextView totalTextView; 


// define an instance variable for tip percent
float tipPercent = .15f;

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

    billAmountEditText = (EditText) findViewById(R.id.billAmountEditText);
    percentTextView = (TextView) findViewById(R.id.percentTextView);
    percentUpButton = (Button) findViewById(R.id.percentUpButton);
    percentDownButton = (Button) findViewById(R.id.percentDownButton);
    tipTextView = (TextView) findViewById(R.id.tipTextView);
    totalTextView = (TextView) findViewById(R.id.totalTextView);

    // set the listeners
    billAmountEditText.setOnEditorActionListener(this);
    percentUpButton.setOnClickListener(this);
    percentDownButton.setOnClickListener(this);
    // calculate the tip and display the results
    calculateAndDisplay();
}

public void calculateAndDisplay() {
    // get the bill amount
    String billAmountString = billAmountEditText.getText().toString();
    float billAmount;
    if (billAmountString.equals("")) {
        billAmount = 0;
    } else {
        billAmount = Float.parseFloat(billAmountString);
    }

    // calculate tip and total
    float tipAmount = billAmount * tipPercent;
    float totalAmount = billAmount + tipAmount;

    // display the results with formatting
    NumberFormat currency = NumberFormat.getCurrencyInstance();
    tipTextView.setText(currency.format(tipAmount));
    totalTextView.setText(currency.format(totalAmount));
    NumberFormat percent = NumberFormat.getPercentInstance();
    percentTextView.setText(percent.format(tipPercent));
}

@Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
    calculateAndDisplay();
    return false;
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
    case R.id.percentDownButton:
        tipPercent = tipPercent - .01f;
        calculateAndDisplay();
        break;
    case R.id.percentUpButton:
        tipPercent = tipPercent + .01f;
        calculateAndDisplay();
        break;
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}
}

Answer 1

You may

1. Go to Project > Properties > Java Build Path > tab [Order and Export] > Tick Android Version Checkbox, and then Properties again > Build Project .

2. Mistakes in your xml views could cause the R.java not to be generated. Go through your view files and make sure all the xml is right

Go to your string.xml under res\\values add one line

<string name="action_settings">Settings</string>

such that:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">Hello Map</string>
    <string name="action_settings">Settings</string>
</resources>