如何从SQLite数据库数据，Android和在TextView中显示它 [英] How to retrieve data from sqlite database in android and display it in TextView
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问题描述
我学习的Android。我有一个问题，我解决不了它。我想从现有的数据库中检索数据并点击按钮后，在的TextView 显示它。
I am learning Android. I have a problem and I can't solve it. I want to retrieve data from an existing database and display it in a TextView after click button.
我的code DataBaseHelper 是这样的：
My code DataBaseHelper looks like this:
public class DataBaseHelper extends SQLiteOpenHelper {
//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/in.ekonomia.android/databases/";
private static String DB_NAME = "cytaty";
private SQLiteDatabase myDataBase;
private final Context myContext;
/** * Constructor * Takes and keeps a reference of the passed context in order to access to the application assets and resources. * @param context */
public DataBaseHelper(Context context)
{
super(context, DB_NAME, null, 1);
this.myContext = context;
}
/** * Creates a empty database on the system and rewrites it with your own database. * */
public void createDataBase() throws IOException
{
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing - database already exist
}else{
//By calling this method and empty database will be created into the default system path
//of your application so we are gonna be able to overwrite that database with our database.
this.getReadableDatabase();
try
{
copyDataBase();
} catch (IOException e)
{
throw new Error("Error copying database");
}
}
}
/** * Check if the database already exist to avoid re-copying the file each time you open the application. * @return true if it exists, false if it doesn't */
private boolean checkDataBase()
{ SQLiteDatabase checkDB = null;
try
{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch (SQLiteException e)
{
//database does't exist yet.
}
if(checkDB != null)
{
checkDB.close();
}
return checkDB != null ? true : false;
}
/** * Copies your database from your local assets-folder to the just created empty database in the * system folder, from where it can be accessed and handled. * This is done by transfering bytestream. * */
private void copyDataBase() throws IOException
{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0)
{
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException {
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close()
{
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db)
{ }
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { }
// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.
}
Cytaty.java 是这样的：
package in.ekonomia.android;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class cytaty extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.galeria);
Button bLosuj = (Button) findViewById(R.id.button1);
bLosuj.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
}
});
}
}
我的上面没有和Eclipse给我的错误。
I did as above and Eclipse gives me errors.
Database name: cytaty
name of table: cytaty
columns: _id, autor, cytat
我的 code 是：
public void getData() {
public String[] getAppCategorydetail() {
String Table_Name="cytaty";
String selectQuery = "SELECT * FROM " + Table_Name;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
String[] data = null;
if (cursor.moveToFirst()) {
do {
// get the data into array,or class variable
} while (cursor.moveToNext());
}
db.close();
return data;
}
}
和
Button bLosuj = (Button) findViewById(R.id.button1);
bLosuj.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
DataBaseHelper myDataBaseHelper = new DataBaseHelper(cytaty.this);
myDataBaseHelper.openDataBase();
String text= myDataBaseHelper.getData();//this is the method to query
myDataBaseHelper.close();
// set text to your TextView
TextView tekst = (TextView) findViewById(R.id.editText1);
tekst.setText(text);
}
});
}
我是什么做错了吗？
我想点击按钮后，从数据库中检索和显示数据的TextView 。您的帮助将是AP preciated。
What am I doing wrong?
I want retrieve data from database and show in TextView after click button. Your help would be appreciated.
推荐答案
在按一下按钮，先打开数据库，获取数据，然后关闭数据库这样
on button click, first open the database, fetch the data and close the data base like this
public class cytaty extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.galeria);
Button bLosuj = (Button) findViewById(R.id.button1);
bLosuj.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
myDatabaseHelper= new DatabaseHelper(cytaty.this);
myDatabaseHelper.openDataBase();
String text= myDatabaseHelper.getyourdata();//this is the method to query
myDatabaseHelper.close();
// set text to your TextView
}
});
}
}
和你的getyourdata（）中的数据库类wouldbe喜欢这种
and your getyourdata() in database class wouldbe like this
public String[] getAppCategorydetail(){
String Table_Name="name of table";
String selectQuery = "SELECT * FROM " + Table_Name;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
String[] data = null;
if (cursor.moveToFirst()) {
do {
// get the data into array,or class variable
} while (cursor.moveToNext());
}
db.close();
return data;
}
这篇关于如何从SQLite数据库数据，Android和在TextView中显示它的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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