Question

我正在尝试使用ListView数据库在主片段中创建sqlite。数据已插入数据库但无法在主片段中显示为ListView。这是我的java和xml文件....

Dbhelper.java

    package jarvis.medicinereminder.database;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import jarvis.medicinereminder.MainActivity;

public class DbHelper extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "reminder.db";
    public static final String TABLE_NAME = "reminder_table";
    public static final String COL1 = "ID";
    public static final String COL2 = "NAME";
    public static final String COL3 = "TIME";
    public static final String COL4 = "DATE";

    public DbHelper(MainActivity context){
        super(context,DATABASE_NAME,null,1);
    }

    @Override
    public void onCreate(SQLiteDatabase db){

        String createTable = "CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +"NAME TEXT," +
                " " +"TIME TEXT, " +"DATE 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 name, String time, String date){
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL2, name);
        contentValues.put(COL3, time);
        contentValues.put(COL4, date);

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

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

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

ViewListContents.java

    package jarvis.medicinereminder.database;

import android.database.Cursor;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
import jarvis.medicinereminder.R;

public class ViewListContents extends AppCompatActivity {

    DbHelper myDB;

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

        ListView listView = (ListView)findViewById(R.id.listView);
        //myDB = new DbHelper(this);

        ArrayList<String> theList = new ArrayList<>();
        Cursor data = myDB.getListContents();

        while (data.moveToNext()){
            theList.add(data.getString(1));
            ListAdapter listAdapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,theList);
            listView.setAdapter(listAdapter);
        }
    }
}

fragment_main.xml

    <?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Main"
        android:id="@+id/textView2"
        android:layout_gravity="center" />

    <ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/listView"
        android:layout_gravity="center" />
</FrameLayout>

Answer 1

请在myDB = new DbHelper(this);

中取消注释oncreate()

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

        ListView listView = (ListView)findViewById(R.id.listView);
        myDB = new DbHelper(this);

        ArrayList<String> theList = new ArrayList<>();
        Cursor data = myDB.getListContents();

        while (data.moveToNext()){
            theList.add(data.getString(1));
            ListAdapter listAdapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,theList);
            listView.setAdapter(listAdapter);
        }
    }

无法在片段中显示listview

1 个答案: