如何从android中的sqlite数据库中检索数据并在TextView中显示

How to retrieve data from sqlite database in android and display it in TextView

提问by Tomeksss

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 TextViewafter click button.

我正在学习安卓。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将其显示TextView在单击按钮后。

My code DataBaseHelperlooks like this:

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.javalooks like this:

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

            }
            });
        }

}

---

---

I did as above and Eclipse gives me errors.

我按上面做了，Eclipse 给了我错误。

Database name: cytaty
name of table: cytaty
columns: _id, autor, cytat 

My codeis:

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;
    }

}

And:

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);
        }
        });
    }

What am I doing wrong? I want retrieve data from database and show in TextViewafter click button. Your help would be appreciated.

我究竟做错了什么？我想从数据库中检索数据并在TextView单击按钮后显示。您的帮助将不胜感激。

回答by Rajendra

on button click, first open the database, fetch the data and close the data base like this

单击按钮时，首先打开数据库，获取数据并像这样关闭数据库

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
            }
        });
    }
}

and your getYourData()in database class would be like this

你getYourData()的数据库类会是这样的

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;
}

回答by Mehdi

You may use this following code actually it is rough but plz check it out

您可以使用以下代码，实际上它很粗糙，但请检查一下

db = openOrCreateDatabase("sms.db", SQLiteDatabase.CREATE_IF_NECESSARY, null);
Cursor cc = db.rawQuery("SELECT * FROM datatable", null);
final ArrayList<String> row1 = new ArrayList<String>();
final ArrayList<String> row2 = new ArrayList<String>();

if(cc!=null) {
    cc.moveToFirst();   
    startManagingCursor(cc);
    for (int i=0; i<cc.getCount(); i++) {

    String number  = cc.getString(0);
    String message = cc.getString(1);
    row1.add(number);
    row2.add(message);

    final EditText et3 = (EditText) findViewById(R.id.editText3);
    final EditText et4 = (EditText) findViewById(R.id.editText4);
    Button bt1 = (Button) findViewById(R.id.button1);
    bt1.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            switch (v.getId()) {
                case R.id.button1:
                    et3.setText(row1.get(count));
                    et4.setText(row2.get(count));
                    count++;
                    break;
                default:
                    break;
            }

        }
    });

cc.moveToNext();
}

回答by ChamalPradeep

TextView tekst = (TextView) findViewById(R.id.editText1); 

You cannot cast EditTextto TextView.

你不能投射EditText到TextView.

回答by ziddi609

First cast your Edit text like this:

首先像这样投射您的编辑文本：

TextView tekst = (TextView) findViewById(R.id.editText1);
tekst.setText(text);

And after that close the DB not befor this line...

然后关闭数据库而不是这条线......

 myDataBaseHelper.close(); 

回答by ziddi609

You are using getData() method as void.

您正在使用 getData() 方法作为 void。

You can not return values from void.

您不能从 void 返回值。