我正在尝试制作一个订购咖啡的应用程序。(我真的很陌生。)

我的应用程序运行良好，直到出现两个错误。现在，它可以在设备中运行，但是当您尝试触摸按钮时，它将停止。

代码是：

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;

//int priceOfOneCup = 5;

@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){

//calculatePrice(quantity, priceOfOneCup);

int price = quantity * 5 ;

String priceMessage = "Total: " + price + "€" + "\nThank You!";

displayMessage(priceMessage);

}

/**

* This method is called when the plus button is clicked.

*/

public void increment(View view) {

quantity = quantity + 1;

displayQuantity(quantity);

}

/**

* This method is called when the minus button is clicked.

*/

public void decrement(View view) {

quantity = quantity - 1;

displayQuantity(quantity);

}

/**

* This method displays the given quantity value on the screen.

*/

private void displayQuantity(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));

}

/**

* 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);

}

XML代码：

xmlns:tools="http://schemas.android.com/tools"

android:id="@+id/activity_main"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

android:padding="16dp"

tools:context="com.example.android.justjava.MainActivity">

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginBottom="16dp"

android:text="Quantity"

android:textAllCaps="true" />

android:layout_width="match_parent"

android:layout_height="wrap_content">

android:layout_width="48dp"

android:layout_height="48dp"

android:onClick="decrement"

android:text="-" />

android:id="@+id/quantity_text_view"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginLeft="8dp"

android:layout_marginRight="8dp"

android:text="0"

android:textColor="@android:color/black"

android:textSize="16sp"

/>

android:layout_width="48dp"

android:layout_height="48dp"

android:onClick="increment"

android:text="+" />

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginBottom="16dp"

android:layout_marginTop="16dp"

android:text="Price"

android:textAllCaps="true" />

android:id="@+id/price_text_view"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Total: 0€"

android:textColor="@android:color/black"

android:textSize="16sp" />

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginTop="16dp"

android:onClick="submitOrder"

android:text="Order" />

终端中的第一个错误：

E/dalvikvm: Could not find class 'android.graphics.drawable.RippleDrawable', referenced from method android.support.v7.widget.AppCompatImageHelper.hasOverlappingRendering

和主要错误：

E/AndroidRuntime: FATAL EXCEPTION: main

Process: com.example.android.justjava, PID: 32585

java.lang.IllegalStateException: Could not execute method for android:onClick

at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)

at android.view.View.performClick(View.java:4508)

at android.view.View$PerformClick.run(View.java:18675)

at android.os.Handler.handleCallback(Handler.java:733)

at android.os.Handler.dispatchMessage(Handler.java:95)

at android.os.Looper.loop(Looper.java:136)

at android.app.ActivityThread.main(ActivityThread.java:5584)

at java.lang.reflect.Method.invokeNative(Native Method)

at java.lang.reflect.Method.invoke(Method.java:515)

at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)

at dalvik.system.NativeStart.main(Native Method)

Caused by: java.lang.reflect.InvocationTargetException

at java.lang.reflect.Method.invokeNative(Native Method)

at java.lang.reflect.Method.invoke(Method.java:515)

at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)

at android.view.View.performClick(View.java:4508)

at android.view.View$PerformClick.run(View.java:18675)

at android.os.Handler.handleCallback(Handler.java:733)

at android.os.Handler.dispatchMessage(Handler.java:95)

at android.os.Looper.loop(Looper.java:136)

at android.app.ActivityThread.main(ActivityThread.java:5584)

at java.lang.reflect.Method.invokeNative(Native Method)

at java.lang.reflect.Method.invoke(Method.java:515)

at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)

at dalvik.system.NativeStart.main(Native Method)

Caused by: android.content.res.Resources$NotFoundException: String resource ID #0x1

at android.content.res.Resources.getText(Resources.java:1404)

at android.support.v7.widget.ResourcesWrapper.getText(ResourcesWrapper.java:52)

at android.widget.TextView.setText(TextView.java:4262)

at com.example.android.justjava.MainActivity.displayQuantity(MainActivity.java:61)

at com.example.android.justjava.MainActivity.increment(MainActivity.java:44)

at java.lang.reflect.Method.invokeNative(Native Method)

at java.lang.reflect.Method.invoke(Method.java:515)

at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)

at android.view.View.performClick(View.java:4508)

at android.view.View$PerformClick.run(View.java:18675)

at android.os.Handler.handleCallback(Handler.java:733)

at android.os.Handler.dispatchMessage(Handler.java:95)

at android.os.Looper.loop(Looper.java:136)

at android.app.ActivityThread.main(ActivityThread.java:5584)

at java.lang.reflect.Method.invokeNative(Native Method)

at java.lang.reflect.Method.invoke(Method.java:515)

at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)

at dalvik.system.NativeStart.main(Native Method)