将sqlite数据库中的所有数据显示到选项卡式活动中的列表视图中 [英] Displaying ALL data from sqlite database into listview in tabbed activity
问题描述
作为 Android 开发的新手，我已经被这个问题困住了几个星期，而且越来越累.
As a newcomer to android development I've been stuck on this issue for a few weeks now and it's getting pretty tiring.
在查看了每个教程并阅读了我能找到的每个问题和答案后，我仍然不知道如何让 Android Studio 只获取我的 SQLite 数据库中的内容并将其内容粘贴到 listview代码>.我原以为在 XML 文件中会有某种 android:displayallfrom("myDB") 命令来显示数据库中的所有内容，但它似乎要复杂得多.
After looking at every tutorial and reading every question and answer I could find, still I can't figure out how to get Android Studio to just take what's in my SQLite database and paste its contents into a listview. I would've thought there would be a android:displayallfrom("myDB") command of some kind in the XML files to just display everything there is in a database but it appears to be much more complicated.
基本上，我想要做的是显示我数据库中的所有数据(Dogs.db)到我的listview(list_dogs) 在我的选项卡视图 (Tab1) 的第一个选项卡中.
Basically, what I want to do is display ALL data from my database (Dogs.db) into my listview (list_dogs) in the first tab of my tab view (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;
}
}
我确定我遗漏了一些非常愚蠢的东西，但任何帮助将不胜感激.
I'm sure there is something really dumb I'm missing but any help would be appreciated.
推荐答案
如果你想在一个ListView中显示每条dog的每一条信息，你需要制作一个 Dog 类.虽然不是必需的，但它会让你的工作更轻松，从数据库中获取数据并将每个 dog 的信息存储在一个 Dog 类实例中会更有意义.
If you want to display each and every information of each dog in a ListView, you need to make a Dog class. Although it is not necessary but it would make your job easier and it would make more sense to get data from database and store the information of each dog in a Dog class instance.
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，该文件将代表您的 ListView 的每一行.您可以随心所欲地设计它.
Then you need to define a layout XML file that will represent the each row of your ListView. You are able to design it any way you want.
这是一个示例行布局代码
<?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，您需要自己的自定义适配器类，该类扩展BaseAdapter 类和OverridegetView 方法.
After this, you need your own custom adapter class that extends the BaseAdapter class and Override the getView method.
这是一个示例自定义适配器类
Here's an example custom adapter class
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.
Now you need to get data from database and store the information of each dog in a separate Dog class instance that you created earlier.
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;
}
现在您的所有数据库数据都存储在 Dog 类的实例中，这些实例存储在 doglist ArrayList 中.
Now all your data from the database is stored in the instances of Dog class that are stored in doglist ArrayList.
最后你需要一个方法来填充你的 ListView
Finally you need a method that fills your ListView
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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