将所有数据从SQLITE数据库中显示到选项卡活动中的ListView中

Question

作为Android开发的新手，我已经在这个问题上一直困扰着几个星期，而且变得非常累人。

查看了每个教程并阅读了我可以找到的每个问题和答案之后，我仍然不知道如何让Android Studio仅将SQLite数据库中的内容粘贴到listview中。我本来以为XML文件中会有某种类型的android:displayallfrom("myDB")命令，以显示数据库中的所有内容，但似乎更为复杂。

基本上，我想做的是在我的 listview（ list_dogs）中显示我数据库（ Dogs.db）的所有数据，在我的TAB视图的第一个选项卡（Tab1）中。

。

这是我的代码：

TAB1.JAVA

package com.example.major.awoo;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Tab1 extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.tab1, container, false);
        return rootView;
    }
}

TAB1.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    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.example.major.awoo.MainActivity">
    <ListView
        android:id="@+id/list_dogs"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:listSelector=""/>
</RelativeLayout>

databasehelper.java

package com.example.major.awoo;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHelper extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "Dogs.db";
    public static final String TABLE_NAME = "dogs_table";
    public static final String COL_1 = "ID";
    public static final String COL_2 = "NAME";
    public static final String COL_3 = "AGE";
    public static final String COL_4 = "WEIGHT";
    public static final String COL_5 = "BREED";
    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
            db.execSQL("create table " + TABLE_NAME +" (ID INTEGER PRIMARY KEY AUTOINCREMENT,NAME TEXT,SURNAME TEXT,MARKS INTEGER)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
        onCreate(db);
    }
    public boolean insertData(String name,String age,String weight,String breed) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL_2,name);
        contentValues.put(COL_3,age);
        contentValues.put(COL_4,weight);
        contentValues.put(COL_5,breed);
        long result = db.insert(TABLE_NAME, null, contentValues);
        if(result == -1)
            return false;
        else
            return true;
    }
    public Cursor getAllData() {
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor res = db.rawQuery("select * from "+TABLE_NAME,null);
        return res;
    }
    public boolean updateData(String id,String name,String age,String weight,String breed) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL_1,id);
        contentValues.put(COL_2,name);
        contentValues.put(COL_3,age);
        contentValues.put(COL_4,weight);
        contentValues.put(COL_5,breed);
        db.update(TABLE_NAME, contentValues, "ID = ?",new String[] { id });
        return true;
    }
    public Integer deleteData (String id) {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.delete(TABLE_NAME, "ID = ?",new String[] {id});
    }
    public Cursor getListContents(){
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor data = db.rawQuery("SELECT * FROM " + TABLE_NAME,null);
        return data;
}
//method to display data
    public Cursor displayData;
    {
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor res = db.rawQuery(" SELECT  * FROM " + TABLE_NAME, null);
        return res;    
    }   
}

我敢肯定，我确实缺少一些愚蠢的东西，但会不胜感激。

Answer 1

如果要在ListView中显示每个dog的每个信息，则需要进行Dog类。尽管不是必需的，但它会使您的工作变得更轻松，并且从数据库中获取数据并将每个dog的信息存储在Dog类实例中更有意义。

public class Dog {
    private String id;
    private String name;
    private String age;
    private String breed;
    private String weight;
    public Dog(String id, String name, String age, String breed, String weight) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.breed = breed;
        this.weight = weight;
    }
    public String getID() {
        return this.id;
    }
    public String getName() {
        return this.name;
    }
    public String getAge() {
        return this.age;
    }
    public String getWeight() {
        return this.weight;
    }
    public String getBreed() {
        return this.breed;
    }
}

然后，您需要定义一个layout XML文件，该文件将代表ListView的每一行。您能够以任何想要的方式设计它。

这是示例行布局代码

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <TextView
        android:id="@+id/text_dogID"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="demo"
        android:textColor="#000"
        android:textSize="25sp"/>
    <TextView
        android:id="@+id/text_dogName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="demo"
        android:textColor="#000"
        android:textSize="25sp"
        app:layout_constraintTop_toBottomOf="@id/text_dogID"/>
    <TextView
        android:id="@+id/text_dogAge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="demo"
        android:textColor="#000"
        android:textSize="25sp"
        app:layout_constraintTop_toBottomOf="@id/text_dogName"/>
    <TextView
        android:id="@+id/text_dogWeight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="demo"
        android:textColor="#000"
        android:textSize="25sp"
        app:layout_constraintTop_toBottomOf="@id/text_dogAge"/>
    <TextView
        android:id="@+id/text_dogBreed"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="demo"
        android:textColor="#000"
        android:textSize="25sp"
        app:layout_constraintTop_toBottomOf="@id/text_dogWeight"/>
</android.support.constraint.ConstraintLayout>

之后，您需要自己的custom adapter类extends BaseAdapter类和Override getView方法。

这是示例自定义适配器类

public class CustomAdapter extends BaseAdapter{
    private ArrayList<Dog> dogsList;
    private Context context;
    public CustomAdapter(ArrayList<Dog> list, Context cont){
        this.dogsList = list;
        this.context = cont;
    }
    @Override
    public int getCount() {
        return this.dogsList.size();
    }
    @Override
    public Object getItem(int position) {
        return this.dogsList.get(position);
    }
    @Override
    public long getItemId(int i) {
        return i;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        if(convertView == null){
            LayoutInflater inf = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inf.inflate(R.layout.listview_row_layout, null);
            holder = new ViewHolder();
            holder.id = (TextView)convertView.findViewById(R.id.text_dogID);
            holder.name = (TextView)convertView.findViewById(R.id.text_dogName);
            holder.age = (TextView)convertView.findViewById(R.id.text_dogAge);
            holder.weight = (TextView)convertView.findViewById(R.id.text_dogWeight);
            holder.breed = (TextView)convertView.findViewById(R.id.text_dogBreed);
            convertView.setTag(holder);
        }
        else {
            holder = (ViewHolder)convertView.getTag();
        }
        Dog stu = dogsList.get(position);
        holder.id.setText(stu.getID());
        holder.name.setText(stu.getName());
        holder.age.setText(stu.getAge());
        holder.weight.setText(stu.getWeight());
        holder.breed.setText(stu.getBreed());
        return convertView;
    }
    private static class ViewHolder{
        public TextView id;
        public TextView name;
        public TextView age;
        public TextView weight;
        public TextView breed;
    }
}

现在，您需要从数据库中获取数据并将每只狗的信息存储在您之前创建的单独的Dog类实例中。

public ArrayList<Dog> getAllData() {
        ArrayList<Dog> doglist = new ArrayList<>();
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor res = db.rawQuery("select * from "+TABLE_NAME,null);
        while(res.moveToNext()) {
            String id = res.getString(0);   //0 is the number of id column in your database table
            String name = res.getString(1);
            String age = res.getString(2);
            String breed = res.getString(3);
            String weight = res.getString(4);
            Dog newDog = new Dog(id, name, age, breed, weight);
            doglist.add(newDog);
        }
        return doglist;
 }

现在，数据库中的所有数据都存储在doglist ArrayList中存储的Dog类的实例中。

最后，您需要一种填充ListView

的方法

public void fillListview() {
     ListView myListview = findViewById(R.id.myListview);
     DatabaseHelper dbhelper = new DatabaseHelper(this);
     ArrayList<Dog> dogList = dbhelper.getAllData();
     Customadapter myAdapter = new Customadapter(dogList, this);
     myListview.setAdapter(myAdapter);
}