我是一名新的Android开发人员，正在研究Udacity Beginners课程中的JustJava应用程序。使用我的手机调试我的代码，当我点击按钮更新价格时，它会给出错误：“不幸的是，JustJava已经停止了。”
的AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android.justjava">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="justjava"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
MainActivity.java
import android.icu.text.NumberFormat;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;
/**
* This app displays an order form to order coffee.
*/
public class MainActivity extends AppCompatActivity {
@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) {
display(2);
displayPrice(2 * 5);
}
/**
* 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));
}
}
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
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"
android:orientation="vertical"
tools:context="com.example.android.justjava.MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="quantity"
android:textAllCaps="true"
android:padding="16dp" />
<TextView
android:id="@+id/quantity_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="0"
android:textSize="16sp"
android:layout_marginLeft="16dp"
android:layout_marginStart="16dp"
android:textColor="@android:color/black"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Price"
android:textAllCaps="true"
android:padding="16dp" />
<TextView
android:id="@+id/price_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="NGN0"
android:textSize="16sp"
android:layout_marginLeft="16dp"
android:layout_marginStart="16dp"
android:textColor="@android:color/black"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ORDER"
android:layout_margin="16dp"
android:onClick="submitOrder"/>
</LinearLayout>
Logcat错误：
04-25 09:22:04.944 449-449/com.example.android.justjava E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.android.justjava, PID: 449
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:4470)
at android.view.View$PerformClick.run(View.java:18773)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5341)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:830)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:646)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:4470)
at android.view.View$PerformClick.run(View.java:18773)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5341)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:830)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:646)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NoClassDefFoundError: android.icu.text.NumberFormat
at com.example.android.justjava.MainActivity.displayPrice(MainActivity.java:49)
at com.example.android.justjava.MainActivity.submitOrder(MainActivity.java:33)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:4470)
at android.view.View$PerformClick.run(View.java:18773)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5341)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
答案 0 :(得分：3)
错误相当具体。根本原因是在堆栈跟踪的末尾：
Caused by: java.lang.NoClassDefFoundError: android.icu.text.NumberFormat
at com.example.android.justjava.MainActivity.displayPrice(MainActivity.java:49)
at com.example.android.justjava.MainActivity.submitOrder(MainActivity.java:33)
类加载器可能找不到您在应用中使用的android.icu.text.NumberFormat类定义
您应该检查手机上安装的Android版本是否与仅从API 24（Android 7.0）开始提供的此类兼容。
https://developer.android.com/reference/android/icu/text/NumberFormat.html