作为Android开发的新手，我已经在这个问题上坚持了几个星期，而且它变得非常累人。
在查看每个教程并阅读我能找到的每个问题和答案之后，我仍然无法弄清楚如何让Android Studio在我的SQLite数据库中使用其中的内容并将其内容粘贴到listview。我会认为XML文件中会有某种android:displayallfrom("myDB")命令只显示数据库中的所有内容，但它看起来要复杂得多。
基本上，我想要做的是在我的数据库中显示所有数据（Dogs.db）到listview（list_dogs）的第一个标签中我的标签视图（Tab1）。
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;
}
}
我确定有一些非常愚蠢的东西我会失踪，但任何帮助都会受到赞赏。
答案 0 :(得分：3)
如果您想在dog中显示每个ListView的每个信息，则需要制作Dog课程。虽然没有必要，但它会使您的工作更轻松，从数据库获取数据并将每个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。您可以按照自己想要的任何方式进行设计。
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>
在此之后，您需要自己的custom adapter课程extends BaseAdapter课程和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，并将每条狗的信息存储在您之前创建的单独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Dog doglist类的实例中，这些实例存储在ArrayList ListView中。
最后，您需要一种填充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);
}
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