在这个项目中，所有功能都能很好地接受删除并显示所有数据。 一旦我删除了记录，之后如果我要插入它，那么它将被插入但我无法看到它。我认为它是在一些先前的索引值之后插入的。所以请告诉我删除所有记录并显示所有记录的错误。 我正在使用光标。我不知道如何通过光标删除和显示所有记录。请告诉我你错在哪里。 项目代码在这里：
package com.example.databaseExample2;
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 DBAdapter
{
public static final String KEY_ROWID = "_id";
public static final String KEY_ISBN = "isbn";
public static final String KEY_TITLE = "title";
public static final String KEY_PUBLISHER = "publisher";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "test";
private static final String DATABASE_TABLE = "titles";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE =
"create table titles (_id integer primary key autoincrement, "
+ "isbn text not null, title text not null, "
+ "publisher text not null);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(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 titles");
onCreate(db);
}
}
//---opens the database---
public DBAdapter 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 isbn, String title, String publisher)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_ISBN, isbn);
initialValues.put(KEY_TITLE, title);
initialValues.put(KEY_PUBLISHER, publisher);
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;
}
// public boolean deleteAllTitle()
// {
// return db.delete(DATABASE_TABLE,null, null);
// }
//---retrieves all the titles---
public Cursor getAllTitles()
{
Cursor mCursor = db.query(DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_ISBN,
KEY_TITLE,
KEY_PUBLISHER},
null,
null,
null,
null,
null);
if (mCursor != null)
{
mCursor.moveToFirst();
}
return mCursor;
}
//---retrieves a particular title---
public Cursor getTitle(long rowId) throws SQLException
{
Cursor mCursor =
db.query(true, DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_ISBN,
KEY_TITLE,
KEY_PUBLISHER
},
KEY_ROWID + "=" + rowId,
null,
null,
null,
null,
null);
if (mCursor != null)
{
mCursor.moveToFirst();
}
return mCursor;
}
public void deleteAll()
{
this.db.delete(DATABASE_TABLE, null, null);
}
//---updates a title---
public boolean updateTitle(long rowId, String isbn,
String title, String publisher)
{
ContentValues args = new ContentValues();
args.put(KEY_ISBN, isbn);
args.put(KEY_TITLE, title);
args.put(KEY_PUBLISHER, publisher);
return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}
另一个档案在这里：
package com.example.databaseExample2;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class DatabaseActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// define resources
final Button display_btn = (Button)findViewById(R.id.test_button);
final EditText number = (EditText)findViewById(R.id.number);
final Button insert = (Button)findViewById(R.id.insert);
final Button delete = (Button)findViewById(R.id.delete);
final Button allDisplay = (Button)findViewById(R.id.all);
final DBAdapter db = new DBAdapter(this); // create new database
allDisplay.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
db.open();
Cursor c = db.getAllTitles();
if (c.moveToLast())
{
// for(int i=0;c.getCount()>0;i++ )
// {
DisplayTitle(c);
//}
}
else
{
Toast.makeText(getApplicationContext(), "No title found", Toast.LENGTH_LONG).show();
}
db.close();
}
});
delete.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
db.open();
Cursor c = db.getAllTitles();
if(c.getCount()>0)
{
db.deleteAll();
}
db.close();
System.out.println("Record Delete.");
Toast.makeText(getApplicationContext(), "Record Delete.", Toast.LENGTH_SHORT).show();
}
});
insert.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
//---add 2 titles---
db.open();
long id;
id = db.insertTitle("128","C-Programming","Dhiren");
id = db.insertTitle("256","Android","Shreyash");
id = db.insertTitle("512","Android","Kandarp");
id = db.insertTitle("1024","Android","Sweta");
db.close();
System.out.println("Record Inserted.");
Toast.makeText(getApplicationContext(), "Record Inserted.", Toast.LENGTH_SHORT).show();
}
});
display_btn.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
//---get a title---
//String id1 = .toString();
if(number.getText().toString().equals(""))
{
Toast.makeText(getApplicationContext(), "Please Enter Any Value...", Toast.LENGTH_LONG).show();
}
else
{
Integer id = (Integer)Integer.parseInt(number.getText().toString());
//System.out.println("The Id is: "+id);
db.open();
Cursor c = db.getTitle(id);
if (c.moveToFirst())
{
DisplayTitle(c);
}
else
{
Toast.makeText(getApplicationContext(), "No title found", Toast.LENGTH_LONG).show();
}
db.close();
}
}
});
}
public void DisplayTitle(Cursor c)
{
Toast.makeText(this,
"id: " + c.getString(0) + "\n" + "ISBN: " + c.getString(1) + "\n" + "TITLE: " + c.getString(2) + "\n" +
"PUBLISHER: " + c.getString(3),Toast.LENGTH_LONG).show();
}
public void DisplayAll(Cursor c)
{
for(int i = 0; c.getCount()!=0;i++)
{
Toast.makeText(this,
"id: " + c.getString(0) + "\n" + "ISBN: " + c.getString(1) + "\n" + "TITLE: " + c.getString(2) + "\n" +
"PUBLISHER: " + c.getString(3),Toast.LENGTH_LONG).show();
c.moveToNext();
}
}
}
请帮我解决这个问题。
答案 0 :(得分：1)
allDisplay.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
db.open();
Cursor c = db.getAllTitles();
while(c.moveToNext())
{
Toast.makeText(DatabaseActivity.this,c.getString(0),Toast.LENGTH_LONG).show();
}
}
});
<强>更新
当你需要删除所有不需要检查其他选项时。只需要调用删除
delete.setOnClickListener（new View.OnClickListener（） {
public void onClick(View v)
{
db.open();
db.deleteAll();
db.close();
System.out.println("Record Delete.");
Toast.makeText(getApplicationContext(), "Record Delete.", Toast.LENGTH_SHORT).show();
}
});
<强>更新
public Cursor getAllTitles()
{
Cursor mCursor = db.query(DATABASE_TABLE, new String[] {
KEY_ROWID,
KEY_ISBN,
KEY_TITLE,
KEY_PUBLISHER},
null,
null,
null,
null,
null);
return mCursor;
}
<强>更新
你已经使用了sqlite自动增量字段。所以它会永远增加，直到它超过最大值。假设你删除了10条记录。如果你下次插入id将是11.它不会从1开始。查看official个文档
答案 1 :(得分：1)
如果将数据插入表中，则表上已打开的游标可能会也可能不会看到新添加的数据。如果关闭，重新打开并适当地重新定位光标，您应该看到新数据。