Question

对于初学者，这组代码有效：）

活动XML //list_data.xml

    <ListView
        android:id="@+id/ListView"
        android:layout_width="368dp"
        android:layout_height="200dp"
        tools:layout_editor_absoluteX="8dp"
        tools:layout_editor_absoluteY="8dp" />

    <RadioGroup
        android:id="@+id/RadioGroup"
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" >

    </RadioGroup>

Database Helper dbHelper.java

package com.example.excgen.taxi;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

/**
 * Created by Excgen on 9/25/2017.
 */

public class dbHelper extends SQLiteOpenHelper {

    private static final String TAG = "databaseHelper";

    private static final String TABLE_NAME = "units";
    private static final String COL1 = "id";
    private static final String COL2 = "plate";

    public dbHelper(Context context){
        super(context, TABLE_NAME, null, 1);

    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTable = "CREATE TABLE "+TABLE_NAME+" (ID INTEGER PRIMARY KEY AUTOINCREMENT, "+COL2+" TEXT)";
        db.execSQL(createTable);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP IF TABLE EXISTS "+TABLE_NAME);
        onCreate(db);
    }
    public boolean addData(String item){
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL2, item);

        Log.d(TAG,"addData: Adding "+item+" to "+TABLE_NAME);

        long result = db.insert(TABLE_NAME,null,contentValues);

        if(result == -1){
            return false;
        }else{
            return true;
        }
    }

    public Cursor getData(){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "SELECT * FROM "+ TABLE_NAME;
        Cursor data = db.rawQuery(query,null);
        return data;
    }
}

活动类listData.java

package com.example.excgen.taxi;

import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.RadioButton;
import android.widget.RadioGroup;

import java.util.ArrayList;

public class listData extends AppCompatActivity {

    public static String TAG = "listDataActivity";
    dbHelper mdbHelper;
    private ListView mlistView;
    private RadioGroup mRadioGroup;
    private RadioButton mRadioButton;

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

        mlistView = (ListView) findViewById(R.id.ListView);
        mdbHelper = new dbHelper(this);
        populateListView();
        populateRadioGroup();
    }

    private void populateListView(){
        Log.d(TAG,"Populate List View; Displaying Data in the List View");
        Cursor data = mdbHelper.getData();
        ArrayList<String> dataList = new ArrayList<>();
        while(data.moveToNext()){
            dataList.add(data.getString(1));
        }
        ListAdapter adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,dataList);
        mlistView.setAdapter(adapter);
    }

    private void populateRadioGroup(){
        Cursor data = mdbHelper.getData();
        ArrayList<String> dataList = new ArrayList<>();
        while(data.moveToNext()){
            dataList.add(data.getString(1));
        }

        for (int i = 0; i < dataList.size()-1; i++) {
            mRadioGroup = (RadioGroup)      findViewById(R.id.RadioGroup);
            mRadioButton  = new RadioButton(this);
            mRadioButton.setId(i);
            mRadioButton.setText(dataList.get(i));
            mRadioGroup.addView(mRadioButton);
        }
    }
}

摘要：数据库值为arraylist，然后为listView或RadioGroup 请注意，此集合无法从数据表中的列ID获取实际“id”。要获取实际ID，请使用data.getString（0），因为data.getString（1）从第二列获取值

现在真正的问题是，这有更简单的方法吗？：d

Answer 1

不是运行循环两次，而是创建两种不同的方法，您可以将它们合并为一种方法，使其简单而有效。

将计数器维护为全局变量并继续更新它，直到获取所有数据库项并将其添加到arraylist中。

private int count=0;

private void populateListView(){

    Log.d(TAG,"Populate List View; Displaying Data in the List View");
    Cursor data = mdbHelper.getData();
    ArrayList<String> dataList = new ArrayList<>();
    while(data.moveToNext()){

        dataList.add(data.getString(1));
        mRadioGroup = (RadioGroup)      findViewById(R.id.RadioGroup);
        mRadioButton  = new RadioButton(this);
        mRadioButton.setId(i);
        mRadioButton.setText(dataList.get(i));
        mRadioGroup.addView(mRadioButton);
        count++;
    }
    ListAdapter adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,dataList);
    mlistView.setAdapter(adapter);
}

如何从数据库Android Studio中填充RadioGroup和ListView

1 个答案: