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這個應用程序能夠運行，但它不能打印數據庫中的數據， 我也不知道數據是否能夠插入或不能。初學者級別的SQLite Android應用程序沒有打印結果
這是MainActivity.java
package com.zikri.sqlitetuto3;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
EditText dataET;
Button addB, delB;
TextView dataTV;
MyDBHandler dbHandler;
String getProduct;
Products products;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
startAndroidApp();
}
public void startAndroidApp(){
dbHandler = new MyDBHandler(this,null,null,1);
dataET = (EditText) findViewById(R.id.dataET);
addB = (Button) findViewById(R.id.addB);
delB = (Button) findViewById(R.id.delB);
dataTV = (TextView) findViewById(R.id.dataTV);
getProduct = dataET.getText().toString();
PrintProduct();
addB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
AddProduct(getProduct);
}
});
delB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DelProduct(getProduct);
}
});
}
public void PrintProduct(){
dataTV.setText(dbHandler.PrintProduct());
dataET.setText("");
}
public void AddProduct(String p){
products = new Products(p);
dbHandler.AddProduct(products);
PrintProduct();
}
public void DelProduct(String p){
dbHandler.DelProduct(p);
PrintProduct();
}
}
這是MyDBHandler.java
package com.zikri.sqlitetuto3;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class MyDBHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "products.db";
private static final String PRODUCT_TABLE = "product";
private static final String COL_ID = "id";
private static final String COL_PRODUCTNAME = "product_name";
public MyDBHandler(Context context,
String name,SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db){
String query = "CREATE TABLE "+PRODUCT_TABLE+" ("+
COL_ID+" INTEGER PRIMARY KEY AUTOINCREMENT, "+
COL_PRODUCTNAME+" TEXT"+");";
db.execSQL(query);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
String query = "DROP IF EXIST "+PRODUCT_TABLE;
db.execSQL(query);
onCreate(db);
}
public void AddProduct(Products products){
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COL_PRODUCTNAME,products.get_productname());
db.insert(PRODUCT_TABLE,null,values);
db.close();
}
public void DelProduct(String product){
SQLiteDatabase db = getWritableDatabase();
String query = "DELETE FROM "+PRODUCT_TABLE+
"WHERE "+COL_PRODUCTNAME+" = "+product+";";
db.execSQL(query);
db.close();
}
public String PrintProduct(){
SQLiteDatabase db = getWritableDatabase();
String printproductstring = "";
String query = "SELECT * FROM "+PRODUCT_TABLE+";";
Cursor cur = db.rawQuery(query,null);
cur.moveToFirst();
while(cur.moveToNext()){
printproductstring =
printproductstring+cur.getString(cur.getColumnIndex("product_name"));
printproductstring = printproductstring + "\n";
}
db.close();
return printproductstring;
}
}
這是Product.java
package com.zikri.sqlitetuto3;
public class Products {
private int _ID;
private String _productname;
public Products() {}
public Products(String productname) {
this._productname = productname;
}
public void set_ID(int _ID) {
this._ID = _ID;
}
public int get_ID() {
return _ID;
}
public void set_productname(String _productname) {
this._productname = _productname;
}
public String get_productname() {
return _productname;
}
}
這是activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android=
"http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.zikri.sqlitetuto3.MainActivity">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="textPersonName"
android:ems="10"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:id="@+id/dataET" />
<Button
android:text="INSERT"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/dataET"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:id="@+id/addB" />
<Button
android:text="Delete"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/addB"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:id="@+id/delB" />
<TextView
android:text="TextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"
android:id="@+id/dataTV" />