java - 简单添加应用程序将无法正常工作“很不幸，…”

我是一个初学者，我需要一些建议。当我尝试在android模拟器中运行下面的Android应用程序时，当我尝试运行它时显示“不幸的是，再次关闭了”。

我不确定为什么它不起作用。

有人可以给我建议吗？
谢谢
马特

JAVA：

package again.we.practice;

import org.apache.cordova.DroidGap;

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

public class AgainActivity extends DroidGap {
/** Called when the activity is first created. */

int counter;
Button add, sub;
TextView display;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView (R.layout.main);
    counter = 0;
    add = (Button) findViewById(R.id.bAdd);
    add = (Button) findViewById(R.id.bSub);
    display = (TextView) findViewById(R.id.tvdisplay);
    add.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {
            // TODO Auto-generated method stub
            counter++;
            display.setText("Your total is " + counter);
        }
    });
    sub.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {
            // TODO Auto-generated method stub
            counter--;
            display.setText("Your total is " + counter);
        }
    });
}
}

XML：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="again.we.practice"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk android:minSdkVersion="7"/>
<supports-screens
android:largeScreens="true"
android:normalScreens="true"
android:smallScreens="true"
android:resizeable="true"
android:anyDensity="true" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_LOCATION_EXTRA_COMMANDS" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.RECEIVE_SMS" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.WRITE_CONTACTS" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.BROADCAST_STICKY" />

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" >
    <activity
        android:label="@string/app_name"
        android:name=".AgainActivity"
        android:configChanges="orientation|keyboardHidden" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

</manifest>

最佳答案

更换

add = (Button) findViewById(R.id.bSub);

与

sub = (Button) findViewById(R.id.bSub);

因为未实例化sub，所以您将获得空指针异常。如果错误没有消失，请打印日志猫，以便我们为您提供帮助。