显示无法反抗R。 我如何解决这个问题？ 如果您需要xml文件来解决问题，请在注释中提问
请帮助 ................................................... ................................................... ................................................... ................................................... ................................................... ................................................... ...... 这是Java代码：
package com.example.android.justjava;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;
import java.text.NumberFormat;
/**
* This app displays an order form to order coffee.
*/
public class MainActivity extends AppCompatActivity {
int quantity = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
/**
* This method is called when the order button is clicked.
*/
public void submitOrder(View view) {
int price= quantity*16;
String priceMessage="total:" + (quantity*16) ;
priceMessage=priceMessage +"\nThank You!";
displayMessage(priceMessage);
}
/**
* This method displays the given text on the screen.
*/
private void displayMessage(String message) {
TextView priceTextView = (TextView) findViewById(R.id.price_text_view);
priceTextView.setText(message);
}
public void increase(View view) {
quantity = quantity + 1;
displayPrice(quantity*16);
display(quantity);
}
public void decrease(View view) {
quantity = quantity - 1;
displayPrice(quantity*16);
display(quantity);
}
/**
* This method displays the given quantity value on the screen.
*/
private void display(int number) {
TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);
quantityTextView.setText("" + number);
}
/**
* This method displays the given price on the screen.
*/
private void displayPrice(int number) {
TextView priceTextView = (TextView) findViewById(R.id.price_text_view);
priceTextView.setText(NumberFormat.getCurrencyInstance().format(number);
}
这是xml文件：:: ................................................... ................................................... ................................................... ................................................... ........................................
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/w"
android:orientation="vertical"
>
<TextView
android:id="@+id/txt1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="20dp"
android:text="Welcome to Ordering Menu"
android:textColor="@android:color/white"
android:textSize="25sp"
app:fontFamily="@font/crafty_girls" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_marginTop="20dp"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageView
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_marginLeft="20dp"
android:src="@drawable/cappo"/>
<Button
android:id="@+id/btn2"
android:layout_width="48dp"
android:layout_height="48dp"
android:textSize="30sp"
android:layout_marginLeft="50dp"
android:layout_marginTop="20dp"
android:onClick="increase"
android:text="+"
android:textColor="@android:color/black"
android:background="@android:color/white" />
<TextView
android:id="@+id/quantity_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginTop="20dp"
android:text="0"
android:textSize="20sp"
android:textColor="@android:color/white" />
<Button
android:id="@+id/btn3"
android:layout_width="50dp"
android:textColor="@android:color/black"
android:background="@android:color/white"
android:layout_height="50dp"
android:textBold="true"
android:layout_marginLeft="10dp"
android:layout_marginTop="20dp"
android:onClick="decrease"
android:textSize="30sp"
android:text="-" />
</LinearLayout>
<TextView
android:id="@+id/kk"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="170dp"
android:text="Price" />
<TextView
android:id="@+id/price_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:layout_marginTop="10dp"
android:text="$0"
android:textColor="#000000" />
<Button
android:id="@+id/btn1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginTop="15dp"
android:onClick="submitOrder"
android:text="ORDER" />
</LinearLayout>
</android.support.constraint.ConstraintLayout>
答案 0 :(得分：0)
对您来说可能不是这种情况，但值得一试，有时Android studio会出现故障，需要关闭/重新打开。您也可以尝试Build> Clean Project。
答案 1 :(得分：0)
尝试从android studio菜单File -> Invalidate Caches and Restart -> Invalidate and Restart
答案 2 :(得分：0)
我是这种开发中的新手，所以我可以在哪里找到此导入列表
所以我可以建议您检查几件事。
import com.example.android.justjava.R