Android在数据库的TextView中显示数据

Question

我创建了一个简单的Android应用程序，询问用户的详细信息，如姓名，号码，血型等，并将其保存在数据库中。这发生在编辑屏幕上的编辑文本中，然后应用程序将在TextView的主活动屏幕中显示所有数据。我已经制作了代码，以便在textview中显示文本，但是当我关闭应用程序并再次打开文本时，文本就会消失并且不再存在，我也试图使文本保留在编辑文本中，如< / p>

姓名：吉姆

但是当我更改屏幕时，例如如果我从MainActivity转到EditScreen，则在编辑屏幕中不再显示该文本。

编辑具有编辑文本的屏幕

package com.example.androidsimpledbapp1;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;


public class EditScreen extends Activity {

/*
 * Code Issues:
 * Data is not being persisted on screen 
 * Also the edit text data is not being persisted 
 * Database is not overwriting row in the DB e.g. GaryJamesJimmy instead of Overwriting 
 * Database needs to retrieve all other rows and display them in the TextView 
 * Will need to implement overwriting functionality on the DB for each row 
 * Is Data even persisting?
 */

EditText firstNameInput;
EditText bloodTypeInput;
EditText contacNameInput;
EditText phoneNumberInput;
EditText relationshipInput;
MyDBHandler dbHandler;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_edit_screen);
    //Setting EditTexts 
    firstNameInput = (EditText) findViewById(R.id.inputname);
    bloodTypeInput = (EditText) findViewById(R.id.inputblood);
    contacNameInput = (EditText) findViewById(R.id.inputcontact);
    phoneNumberInput = (EditText) findViewById(R.id.inputnum);
    relationshipInput = (EditText) findViewById(R.id.inputraltion);
    //Setting DbHandler object 
    dbHandler = new MyDBHandler(this, null, null, 1);

}

public void saveMe(View v){
    /*
     * Making a new object 
     * Object takes 5 parameters 
     */
    Details detail = new Details(firstNameInput.getText().toString(),
            bloodTypeInput.getText().toString(),
            contacNameInput.getText().toString(),
            phoneNumberInput.getText().toString(),
            relationshipInput.getText().toString());
    dbHandler.addProduct(detail);

    //Sending Text To Main Activity
    String dbString = dbHandler.databaseToString();
    Intent myIntent = new Intent(v.getContext(),MainActivity.class);
    myIntent.putExtra("mytext",dbString);
    startActivity(myIntent);
    //End of Sending to Main Activity


    //Settint the text in Edit Text
    firstNameInput.setText(dbString);
}


public void clearBtnPressed(View v){
    dbHandler.deleteProducts();
}
}

主要活动 - 这是包含文本视图的屏幕，其中显示文本

package com.example.androidsimpledbapp1;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;



public class MainActivity extends Activity {

TextView mTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //Grabs the TextView 
    mTextView = (TextView)findViewById(R.id.dbname);
    mTextView.setText(getIntent().getStringExtra("mytext"));
}

//Changing Activity
public void editBtnPressed(View v){
    Intent intent = new Intent(MainActivity.this, EditScreen.class);
    startActivity(intent);
}

}

数据库类

package com.example.androidsimpledbapp1;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.Cursor;
import android.content.Context;
import android.content.ContentValues;

public class MyDBHandler extends SQLiteOpenHelper {

/*
 * Class for Working with DB 
 */

//Update each time DB structure changes e.g. adding new property
private static final int DATABASE_VERSION =1;
//DB Name
private static final String DATABASE_NAME = "details.db";
//Table name
public static final String  TABLE_PRODUCTS = "products";
//DB Columns 
public static final String  COLUMN_ID = "_Id";
public static final String  COLUMN_PERSONNAME  = "firstName";
public static final String  COLUMN_PERSONBLOOD  = "bloodType";
public static final String  COLUMN_PERSONCONTACT  = "contactName";
public static final String  COLUMN_PERSONNUMBER  = "phoneNumber";
public static final String  COLUMN_PERSONRELATION = "relationship";

//Constructor
/*
 * Passing information to super class in SQL
 * Context is background information 
 * name of db 
 * Database version
 */
public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version){
    super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}

/*
 * What to do first time when you create DB
 * Creates the table the very first time
 * (non-Javadoc)
 * @see android.database.sqlite.SQLiteOpenHelper#onCreate(android.database.sqlite.SQLiteDatabase)
 * Remember to use Commas as shown below
 */
@Override
public void onCreate(SQLiteDatabase db){
    String query = "CREATE TABLE "+ TABLE_PRODUCTS + "(" +
            COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "+
            COLUMN_PERSONNAME + " TEXT, "+
            COLUMN_PERSONBLOOD + " TEXT, "+
            COLUMN_PERSONCONTACT + " TEXT, "+
            COLUMN_PERSONNUMBER + " TEXT, " +
            COLUMN_PERSONRELATION + " TEXT " +
            ");";
    //Execute the query
    db.execSQL(query);
}

/*
 * If ever upgrading DB call this method
 * (non-Javadoc)
 * @see android.database.sqlite.SQLiteOpenHelper#onUpgrade(android.database.sqlite.SQLiteDatabase, int, int)
 */
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
    //Delete the current table
    db.execSQL("DROP TABLE IF EXISTS" + TABLE_PRODUCTS);
    //create new table 
    onCreate(db);
}

//Add new row to the database
public void addProduct(Details details){
    //Built in class - set values for different columns 
    //Makes inserting rows quick and easy
    ContentValues values = new ContentValues();
    values.put(COLUMN_PERSONNAME, details.get_firstName());
    values.put(COLUMN_PERSONBLOOD, details.get_bloodType());
    values.put(COLUMN_PERSONCONTACT, details.get_contactName());
    values.put(COLUMN_PERSONNUMBER, details.get_phoneNumber());
    values.put(COLUMN_PERSONRELATION, details.get_relationship());
    SQLiteDatabase db = getWritableDatabase();
    db.insert(TABLE_PRODUCTS, null, values);
    db.close();
}

/*Updating Rows in the Database
public void updateProducts(Details details){
    ContentValues cv = new ContentValues();
    SQLiteDatabase db = getWritableDatabase();
    db.update(TABLE_PRODUCTS, cv, COLUMN_ID  + "=" + 1, null);
}
*/

/*Table was deleted*/
public void deleteProducts(){
    SQLiteDatabase db = getWritableDatabase();      
    db.delete(TABLE_PRODUCTS, null, null);
}

//Take DB and Convert to String 
public String databaseToString(){
    String dbString = "";
    SQLiteDatabase db = getWritableDatabase();
    //Every Column and row
    String query = "SELECT * FROM " + TABLE_PRODUCTS + " WHERE 1";

    //Cursor points to a location in your results
    //First row point here, second row point here

    Cursor c = db.rawQuery(query, null);
    c.moveToFirst();

    while(!c.isAfterLast()){
        //Extracts first name and adds to string
        if(c.getString(c.getColumnIndex("firstName"))!=null){
            dbString += c.getString(c.getColumnIndex("firstName"));
            c.moveToNext();
            /*
             * Displaying all other columns 
             */
        }
    }
    db.close();
    return dbString;
}
  }

详细信息类

package com.example.androidsimpledbapp1;

public class Details {

//primary key
private int _id;
//Properties 
private String _firstName;
private String _bloodType;
private String _contactName;
private String _phoneNumber;
private String _relationship;

//Dont Have to Enter Everything each time
public Details(){

}

public Details(String firstName){
    this.set_firstName(firstName);
}

//Passing in details 
//Setting values from the user 
public Details(String firstName, String bloodType,
        String contactName, String phoneNumber,
        String relationship){
    this.set_firstName(firstName);
    this.set_bloodType(bloodType);
    this.set_contactName(contactName);
    this.set_phoneNumber(phoneNumber);
    this.set_relationship(relationship);

}

//Retrieve the data 
public int get_id() {
    return _id;
}

//Setter allows to give property
public void set_id(int _id) {
    this._id = _id;
}

public String get_firstName() {
    return _firstName;
}

public void set_firstName(String _firstName) {
    this._firstName = _firstName;
}

public String get_bloodType() {
    return _bloodType;
}

public void set_bloodType(String _bloodType) {
    this._bloodType = _bloodType;
}

public String get_contactName() {
    return _contactName;
}

public void set_contactName(String _contactName) {
    this._contactName = _contactName;
}

public String get_phoneNumber() {
    return _phoneNumber;
}

public void set_phoneNumber(String _phoneNumber) {
    this._phoneNumber = _phoneNumber;
}

public String get_relationship() {
    return _relationship;
}

public void set_relationship(String _relationship) {
    this._relationship = _relationship;
}

}

Answer 1

当您切换应用时，它处于暂停状态，这可能是导致问题的原因。

我建议您在onPause状态下搜索“保存活动”