如何从android中的sqlite数据库中检索数据并在TextView中显示 [英] How to retrieve data from sqlite database in android and display it in TextView
问题描述
我正在学习 Android.我有一个问题,我无法解决它.我想从现有数据库中检索数据并在单击按钮后将其显示在 TextView
中.
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.
我的代码DataBaseHelper如下所示:
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 看起来像这样:
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
}
});
}
}
<小时>
我按照上面的方法做了,Eclipse 给了我错误.
I did as above and Eclipse gives me errors.
Database name: cytaty
name of table: cytaty
columns: _id, autor, cytat
我的代码是:
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;
}
}
还有:
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);
}
});
}
我做错了什么?我想从数据库中检索数据并在单击按钮后显示在 TextView
中.您的帮助将不胜感激.
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
点击按钮,首先打开数据库,取数据,然后关闭数据库
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) {
super.onCreate(savedInstanceState);
setContentView(R.layout.galeria);
Button bLosuj = (Button) findViewById(R.id.button1);
bLosuj.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
myDatabaseHelper = new DatabaseHelper(cytaty.this);
myDatabaseHelper.openDataBase();
String text = myDatabaseHelper.getYourData(); //this is the method to query
myDatabaseHelper.close();
// set text to your TextView
}
});
}
}
和你在数据库类中的 getYourData()
将是这样的
and your getYourData()
in database class would be like this
public String[] getAppCategoryDetail() {
final 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());
}
cursor.close();
return data;
}
这篇关于如何从android中的sqlite数据库中检索数据并在TextView中显示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!