一个很简单的程序 报空指针异常 实在找不到 大家帮忙看一下

[qq_36121161]

package com.example.testsql;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity{
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper=new MyDatabaseHelper(this,"BookStore.db",null,1);
Button createDatabase=(Button)findViewById(R.id.create_database);
createDatabase.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
dbHelper.getWritableDatabase();
}
});
}

}


package com.example.testsql;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.widget.Toast;
import android.database.sqlite.SQLiteOpenHelper;

public class MyDatabaseHelper extends SQLiteOpenHelper{
public static final String CREATE_BOOK="create table Book("+"id integer primary key autoincrement,"
+ "author text,"+"price real,"+"pages integer,"+"name text)";
private Context mContext;
public MyDatabaseHelper(Context context,String name,CursorFactory factory,int version)
{
super(context,name,factory,version);
mContext=context;
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(CREATE_BOOK);
Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion)
{

}
}

[香辣小龙人]

你这我段代码运行了下，没问题，看看是不是你的mainactivy在mainfest.xml里注册的不对，检查一下包名路径等

[qq_36121161]

引用 1 楼 u014366834 的回复:

你这我段代码运行了下，没问题，看看是不是你的mainactivy在mainfest.xml里注册的不对，检查一下包名路径等

我新建了一个也不行 manifest应该没问题 是不是AVD的问题啊 - - <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.testsql" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="19" /> <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name=".MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>