更新行而不是创建新的条目数据库android
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我一直在研究Android食谱书中的食谱,以利用数据库来存储事件.当前代码允许我添加新条目,但是我无法修改任何添加的条目.我需要的是具有预定行数(48)的数据库,并具有通过相应的edittext字段更新这些行的功能.谁能帮我修改以下代码来实现这一目标？我是android编码的新手,我需要从此数据库开始.
这是我的MyDB文件：
package com.cookbook.data;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.util.Log;
public class MyDB {
private SQLiteDatabase db;
private final Context context;
private final MyDBhelper dbhelper;
// Initializes MyDBHelper instance
public MyDB(Context c){
context = c;
dbhelper = new MyDBhelper(context, Constants.DATABASE_NAME, null,
Constants.DATABASE_VERSION);
}
// Closes the database connection
public void close()
{
db.close();
}
// Initializes a SQLiteDatabase instance using MyDBhelper
public void open() throws SQLiteException
{
try {
db = dbhelper.getWritableDatabase();
} catch(SQLiteException ex) {
Log.v("Open database exception caught", ex.getMessage());
db = dbhelper.getReadableDatabase();
}
}
// Saves a diary entry to the database as name-value pairs in ContentValues instance
// then passes the data to the SQLitedatabase instance to do an insert
public long insertdiary(String title, String content)
{
try{
ContentValues newTaskValue = new ContentValues();
newTaskValue.put(Constants.TITLE_NAME, title);
newTaskValue.put(Constants.CONTENT_NAME, content);
newTaskValue.put(Constants.DATE_NAME, java.lang.System.currentTimeMillis());
return db.insert(Constants.TABLE_NAME, null, newTaskValue);
} catch(SQLiteException ex) {
Log.v("Insert into database exception caught",
ex.getMessage());
return -1;
}
}
// Reads the diary entries from database, saves them in a Cursor class and returns it from the method
public Cursor getdiaries()
{
Cursor c = db.query(Constants.TABLE_NAME, null, null,
null, null, null, null);
return c;
}
}
这是我的MyDBhelper文件：
package com.cookbook.data;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class MyDBhelper extends SQLiteOpenHelper{
private static final String CREATE_TABLE="create table "+
Constants.TABLE_NAME+" ("+
Constants.KEY_ID+" integer primary key autoincrement, "+
Constants.TITLE_NAME+" text not null, "+
Constants.CONTENT_NAME+" text not null, "+
Constants.DATE_NAME+" long);";
// database initialization
public MyDBhelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.v("MyDBhelper onCreate","Creating all the tables");
try {
db.execSQL(CREATE_TABLE);
} catch(SQLiteException ex) {
Log.v("Create table exception", ex.getMessage());
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion) {
Log.w("TaskDBAdapter", "Upgrading from version "+oldVersion
+" to "+newVersion
+", which will destroy all old data");
db.execSQL("drop table if exists "+Constants.TABLE_NAME);
onCreate(db);
}
}
这是我的常量文件：
package com.cookbook.data;
public class Constants {
public static final String DATABASE_NAME="datastorage";
public static final int DATABASE_VERSION=1;
public static final String TABLE_NAME="diaries";
public static final String TITLE_NAME="title";
public static final String CONTENT_NAME="content";
public static final String DATE_NAME="recorddate";
public static final String KEY_ID="_id";
public static final String TABLE_ROW="row_id";
}
这是我的日记文件,可在数据库中创建新条目：
package com.example.classorganizer;
import android.app.Activity;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import com.cookbook.data.MyDB;
import com.cookbook.data.MyDBhelper;
public class Diary extends Activity {
EditText titleET1,contentET1;
EditText titleET2,contentET2;
Button submitBT;
MyDB dba;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.diary);
dba = new MyDB(this);
dba.open();
titleET1 = (EditText)findViewById(R.id.diary1);
contentET1 = (EditText)findViewById(R.id.diarycontentText1);
titleET2 = (EditText)findViewById(R.id.diary2);
contentET2 = (EditText)findViewById(R.id.diarycontentText2);
submitBT = (Button)findViewById(R.id.submitButton);
submitBT.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
try {
saveItToDB();
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public void saveItToDB() {
dba.insertdiary(titleET1.getText().toString(), contentET1.getText().toString());
dba.insertdiary(titleET2.getText().toString(), contentET2.getText().toString());
dba.close();
titleET1.setText("");
contentET1.setText("");
titleET2.setText("");
contentET2.setText("");
Intent i = new Intent(Diary.this, DisplayDiaries.class);
startActivity(i);
}
/** Called when the user clicks the Back button */
public void visitMonday(View view) {
Intent intent = new Intent(this, Monday.class);
startActivity(intent);
}
}
最后是我的DisplayDiaries文件,该文件在列表视图中返回创建的日记：
package com.example.classorganizer;
import java.util.Date;
import java.text.DateFormat;
import java.util.ArrayList;
import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import com.cookbook.data.Constants;
import com.cookbook.data.MyDB;
public class DisplayDiaries extends ListActivity {
MyDB dba;
DiaryAdapter myAdapter;
private class MyDiary{
public MyDiary(String t, String c, String r){
title=t;
content=c;
recorddate=r;
}
public String title;
public String content;
public String recorddate;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
dba = new MyDB(this);
dba.open();
setContentView(R.layout.diaries);
super.onCreate(savedInstanceState);
myAdapter = new DiaryAdapter(this);
this.setListAdapter(myAdapter);
}
private class DiaryAdapter extends BaseAdapter {
private LayoutInflater mInflater;
private ArrayList<MyDiary> diaries;
public DiaryAdapter(Context context) {
mInflater = LayoutInflater.from(context);
diaries = new ArrayList<MyDiary>();
getdata();
}
public void getdata(){
Cursor c = dba.getdiaries();
startManagingCursor(c);
if(c.moveToFirst()){
do{
String title =
c.getString(c.getColumnIndex(Constants.TITLE_NAME));
String content =
c.getString(c.getColumnIndex(Constants.CONTENT_NAME));
DateFormat dateFormat =
DateFormat.getDateTimeInstance();
String datedata = dateFormat.format(new
Date(c.getLong(c.getColumnIndex(
Constants.DATE_NAME))).getTime());
MyDiary temp = new MyDiary(title,content,datedata);
diaries.add(temp);
} while(c.moveToNext());
}
}
@Override
public int getCount() {return diaries.size();}
public MyDiary getItem(int i) {return diaries.get(i);}
public long getItemId(int i) {return i;}
public View getView(int arg0, View arg1, ViewGroup arg2) {
final ViewHolder holder;
View v = arg1;
if ((v == null) || (v.getTag() == null)) {
v = mInflater.inflate(R.layout.diaryrow, null);
holder = new ViewHolder();
holder.mTitle = (TextView)v.findViewById(R.id.name);
holder.mDate = (TextView)v.findViewById(R.id.datetext);
v.setTag(holder);
} else {
holder = (ViewHolder) v.getTag();
}
holder.mdiary = getItem(arg0);
holder.mTitle.setText(holder.mdiary.title);
holder.mDate.setText(holder.mdiary.recorddate);
v.setTag(holder);
return v;
}
public class ViewHolder {
MyDiary mdiary;
TextView mTitle;
TextView mDate;
}
}
/** Called when the user clicks the Back button */
public void visitDiary(View view) {
Intent intent = new Intent(this, Diary.class);
startActivity(intent);
}
}
正如我之前提到的,此代码在运行时允许创建新日记并将其放在列表视图中.我需要修改此代码,以便数据库具有预定义的48行(默认为空),并且日记文件允许通过相应的48个edittext字段来修改行.以上任何帮助将不胜感激.我期待着您的学习.干杯,帕特里克
编辑 – – – – – – – – – – – – – – – – – – – – – – – – – ————————————-
因为我是一个绝对的初学者,所以我仍然无法在表中创建默认的48行,然后编写代码以使用相应的edittext更新每一行.也许有一些乐于助人的灵魂可以为我解决这个问题？
编辑2 ———————————————— ———————————–
我已经用您的代码更新了MyDBhelper onCreate方法,如下所示：
@Override
public void onCreate(SQLiteDatabase db) {
Log.v("MyDBhelper onCreate","Creating all the tables");
ContentValues cv=new ContentValues();
cv.put(Constants.KEY_ID, 1);
cv.put(Constants.TITLE_NAME, "My App");
db.insert( Constants.TABLE_NAME, null, cv);
String Updatetable= "update" + Constants.TABLE_NAME +
"Set" + Constants.CONTENT_NAME + " = " + 1 +
"Where" +Constants.KEY_ID +" = " + R.id.diary1;
try {
db.execSQL(CREATE_TABLE);
} catch(SQLiteException ex) {
Log.v("Create table exception", ex.getMessage());
}
}
但是在Diary的onCreate上创建了新行,而不是更新现有行…在这里我在做什么错？我相信我将代码放置在错误的位置,或者错过了其他东西…
解决方法:
我不确定如何处理48个编辑文本,但是下面的示例将为您提供编写更新查询的想法.
String Updatetable= "update " + Constants.TABLE_NAME + "Set " + Constants.CONTENT_NAME + " = " + your value + "Where " +Constants.KEY_ID +" = " + <<May be your edit text value>> +
将上面的查询写在要更新值的位置
编辑 – – – – – – – – – – – – – – – – – – – – – – – – – ——————————————-
首先,您需要具有这些行应包含的内容的数据,然后才有多种将数据插入数据的方法.
>使用内容值
ContentValues cv = new ContentValues();
cv.put(Constants.KEY_ID,1);
cv.put(Constants.TITLE_NAME,“我的应用”)；
db.insert(Constants.TABLE_NAME,null,cv);
>如上所述编写查询(更新查询)并使用任何方法rawquery,execsql
db.rawQuery(<<您的插入查询>> ;,空)
以同样的方式execsql
要获取更多信息,请检查android documentationable. link
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