您好我正在编写一个用户能够查看的数据库，其中包含有关我填充数据库的数据的信息。在我的手机或模拟器上运行活动时，应用程序崩溃。没有logcat问题所以我不确定可能是什么问题。如果有人能提供任何提示，我会非常感激，因为我刚接触java编程和使用Android ADT。以下是我的活动代码。我正在使用的当前版本是Build：v21.1.0-569685
创建数据库的主要活动：
package com.example.database;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class MainActivity
{
public static final String KEY_ROWID = "_id";
public static final String KEY_BUSINESS = "business";
public static final String KEY_ADDRESS = "address";
public static final String KEY_PHONE = "phone";
public static final String KEY_HOURS = "hours";
public static final String KEY_WEB = "website";
public static final String KEY_TYPE = "type";
private static final String TAG = "MainActivity";
private static final String DATABASE_NAME = "BloomBusiness";
private static final String DATABASE_TABLE = "Business";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE =
"create table Business (_id integer primary key autoincrement, "
+"business text not null, address text not null, hours text not null"+"web text not null"+"type text not null"
+ "phone text not null);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public MainActivity(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(DATABASE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion
+ " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS Business");
onCreate(db);
}
}
//---opens the database---
public MainActivity open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database---
public void close()
{
DBHelper.close();
}
//---insert a title into the database---
public long insertTitle(String business, String address, String phone, String hours, String website, String type)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_BUSINESS, business);
initialValues.put(KEY_ADDRESS, address);
initialValues.put(KEY_PHONE, phone);
initialValues.put(KEY_HOURS, hours);
initialValues.put(KEY_WEB, website);
initialValues.put(KEY_TYPE, type);
return db.insert(DATABASE_TABLE, null, initialValues);
}
//---deletes a particular title---
public boolean deleteTitle(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID +
"=" + rowId, null) > 0;
}
//---retrieves all the titles---
public Cursor getAllTitles()
{
return db.query(DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_BUSINESS,
KEY_ADDRESS,
KEY_PHONE,
KEY_HOURS,
KEY_WEB,
KEY_TYPE},
null,
null,
null,
null,
null);
}
//---retrieves a particular title---
public Cursor getTitle(long rowId) throws SQLException
{
Cursor mCursor =
db.query(DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_BUSINESS,
KEY_ADDRESS,
KEY_PHONE,
KEY_HOURS,
KEY_WEB,
KEY_TYPE},
KEY_ROWID + "=" + rowId,
null,
null,
null,
null,
null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//---updates a title---
public boolean updateTitle(long rowId, String business,
String address, String phone, String hours, String website,String type)
{
ContentValues args = new ContentValues();
args.put(KEY_BUSINESS, business);
args.put(KEY_ADDRESS, address);
args.put(KEY_PHONE, phone);
args.put(KEY_HOURS,hours);
args.put(KEY_WEB, website);
args.put(KEY_TYPE, type);
return db.update(DATABASE_TABLE, args,
KEY_ROWID + "=" + rowId, null) > 0;
}
}
返回所有商家名称的列表：
package com.example.database;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.Toast;
public class DBUse extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MainActivity db = new MainActivity(this);
db.open();
Cursor c = db.getAllTitles();
if(c.moveToFirst())
{
do{DisplayTitle(c);
}while (c.moveToNext());
}
db.open();
Cursor b = db.getTitle(1);
if (b.moveToFirst())
DisplayTitle(c);
else
Toast.makeText(this,"No business found",Toast.LENGTH_LONG).show();
db.close();
db.close();
}
public void DisplayTitle(Cursor c) {
Toast.makeText(this,
"Name: " + c.getString(1)+"\n"+
"Address:" + c.getString(2)+"\n"+
"Phone:" + c.getString(3)+"\n"+
"Hours:" + c.getString(4)+"\n",
Toast.LENGTH_LONG).show();
}
}
将数据输入数据库：
package com.example.database;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.Toast;
public class DBUse extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MainActivity db = new MainActivity(this);
db.open();
Cursor c = db.getAllTitles();
if(c.moveToFirst())
{
do{DisplayTitle(c);
}while (c.moveToNext());
}
db.open();
Cursor b = db.getTitle(1);
if (b.moveToFirst())
DisplayTitle(c);
else
Toast.makeText(this,"No business found",Toast.LENGTH_LONG).show();
db.close();
db.close();
}
public void DisplayTitle(Cursor c) {
Toast.makeText(this,
"Name: " + c.getString(1)+"\n"+
"Address:" + c.getString(2)+"\n"+
"Phone:" + c.getString(3)+"\n"+
"Hours:" + c.getString(4)+"\n",
Toast.LENGTH_LONG).show();
}
}
最后清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.database"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme"
android:debuggable="true">
<activity
android:name="com.example.database.DBUse"
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>
更改清单后，我在控制台中收到此错误，但没有任何内容显示在logcat中。
[2013-04-10 23:46:43 - database] Performing com.example.database.MainActivity activity launch
[2013-04-10 23:46:47 - database] Application already deployed. No need to reinstall.
[2013-04-10 23:46:47 - database] Starting activity com.example.database.MainActivity on device 0A3BB5F106008016
[2013-04-10 23:46:48 - database] New package not yet registered with the system. Waiting 3 seconds before next attempt.
[2013-04-10 23:46:51 - database] Starting activity com.example.database.MainActivity on device 0A3BB5F106008016
[2013-04-10 23:46:51 - database] New package not yet registered with the system. Waiting 3 seconds before next attempt.
[2013-04-10 23:46:54 - database] Starting activity com.example.database.MainActivity on device 0A3BB5F106008016
[2013-04-10 23:46:54 - database] New package not yet registered with the system. Waiting 3 seconds before next attempt.
[2013-04-10 23:46:57 - database] Starting activity com.example.database.MainActivity on device 0A3BB5F106008016
[2013-04-10 23:46:58 - database] New package not yet registered with the system. Waiting 3 seconds before next attempt.
[2013-04-10 23:47:01 - database] Starting activity com.example.database.MainActivity on device 0A3BB5F106008016
[2013-04-10 23:47:01 - database] ActivityManager: Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.example.database/.MainActivity }
[2013-04-10 23:47:01 - database] ActivityManager: Error type 3
[2013-04-10 23:47:01 - database] ActivityManager: Error: Activity class {com.example.database/com.example.database.MainActivity} does not exist.
答案 0 :(得分：0)
应将您的清单改为
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme"
android:debuggable="true">
<activity
android:name="com.example.database.DBUse"
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>
MainActivity不会扩展Activity，应该称之为DbAdapter。