Question

我正在Android中开发一个应用程序，并且在将数据从数据库传递到listview并查看它时遇到问题。

这是我的所有方法的数据库类：

package com.example.admin.planesproject;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.example.admin.planesproject.TodoTask;

public class PlanesDb {

private static final int DB_VERSION = 1;
private static final String DB_NAME = "database.db";
private static final String DB_TODO_TABLE = "PlanesDb";

//columns

public static final String KEY_ID = "_id";
public static final String ID_OPTIONS = "INTEGER PRIMARY KEY AUTOINCREMENT";
public static final int ID_COLUMN = 0;

public static final String KEY_DATE = "date";
public static final String DATE_OPTIONS = "TEXT NOT NULL";
public static final int DATE_COLUMN = 1;

public static final String KEY_DIRECTION = "direction";
public static final String DIRECTION_OPTIONS = "TEXT NOT NULL";
public static final int DIRECTION_COLUMN = 2;

public static final String KEY_MODEL = "model";
public static final String MODEL_OPTIONS = "TEXT";
public static final int MODEL_COLUMN = 3;

public static final String KEY_AIRLINES = "airlines";
public static final String AIRLINES_OPTIONS = "TEXT";
public static final int AIRLINES_COLUMN = 4;

public static final String KEY_FROM = "from";
public static final String FROM_OPTIONS = "TEXT";
public static final int FROM_COLUMN = 5;

public static final String KEY_TO = "to";
public static final String TO_OPTIONS = "TEXT";
public static final int TO_COLUMN = 6;

private static final String DB_CREATE_TODO_TABLE =
        "CREATE TABLE " + DB_TODO_TABLE + "( " +
                KEY_ID + " " + ID_OPTIONS + ", " +
                KEY_DATE + " " + DATE_OPTIONS + ", " +
                KEY_DIRECTION + " " + DIRECTION_OPTIONS + ", " +
                KEY_MODEL + " " + MODEL_OPTIONS + ", " +
                KEY_AIRLINES + " " + AIRLINES_OPTIONS + ", " +
                KEY_FROM + " " + FROM_OPTIONS + ", " +
                KEY_TO + " " + TO_OPTIONS + ");";

private static final String DROP_TODO_TABLE =
        "DROP TABLE IF EXISTS " + DB_TODO_TABLE;

private SQLiteDatabase db;
private Context context;
private DatabaseHelper dbHelper;

private static class DatabaseHelper extends SQLiteOpenHelper {
    public DatabaseHelper(Context context, String name,
                          SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(DB_CREATE_TODO_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL(DROP_TODO_TABLE);
        onCreate(db);
    }
}

public PlanesDb(Context context) {
    this.context = context;
}

public PlanesDb open(){
    dbHelper = new DatabaseHelper(context, DB_NAME, null, DB_VERSION);
    db = dbHelper.getWritableDatabase();
    return this;
}

public void close() {
    dbHelper.close();
}

public long insertTodo(String date, String direction, String model, String airlines, String from, String to) {
    ContentValues newTodoValues = new ContentValues();
    newTodoValues.put(KEY_DATE, date);
    newTodoValues.put(KEY_DIRECTION, direction);
    newTodoValues.put(KEY_MODEL, model);
    newTodoValues.put(KEY_AIRLINES, airlines);
    newTodoValues.put(KEY_FROM, from);
    newTodoValues.put(KEY_TO, to);
    return db.insert(DB_TODO_TABLE, null, newTodoValues);
}

public boolean updateTodo(TodoTask task) {
    long id = task.getId();
    String date = task.getDate();
    String direction = task.getDirection();
    String model = task.getModel();
    String airlines = task.getAirlines();
    String from = task.getFrom();
    String to = task.getTo();
    return updateTodo(id, date, direction, model, airlines, from, to);
}

public boolean updateTodo(long id, String date, String direction, String model, String airlines, String from, String to) {
    String where = KEY_ID + "=" + id;
    ContentValues updateTodoValues = new ContentValues();
    updateTodoValues.put(KEY_DATE, date);
    updateTodoValues.put(KEY_DIRECTION, direction);
    updateTodoValues.put(KEY_MODEL, model);
    updateTodoValues.put(KEY_AIRLINES, airlines);
    updateTodoValues.put(KEY_FROM, from);
    updateTodoValues.put(KEY_TO, to);
    return db.update(DB_TODO_TABLE, updateTodoValues, where, null) > 0;
}

public boolean deleteTodo(long id){
    String where = KEY_ID + "=" + id;
    return db.delete(DB_TODO_TABLE, where, null) > 0;
}

public Cursor getAllTodos() {
    String[] columns = {KEY_ID, KEY_DATE, KEY_DIRECTION, KEY_MODEL, KEY_AIRLINES, KEY_FROM, KEY_TO};
    return db.query(DB_TODO_TABLE, columns, null, null, null, null, null);
}
}

我希望列表视图显示我桌子上的所有内容，但我无法掌握如何操作。教程没什么帮助，因为大多数教程只展示了如何使用一行数据库。

我的ToDo任务包含所有的getter和setter：

public class TodoTask {
private long id;
private String date;
private String direction;
private String model;
private String airlines;
private String from;
private String to;

public TodoTask(long id, String date, String direction, String model, String airlines, String from, String to) {
    this.id = id;
    this.date = date;
    this.direction = direction;
    this.model = model;
    this.airlines = airlines;
    this.from = from;
    this.to = to;
}

public long getId() {
    return id;
}

public void setId(long id) {
    this.id = id;
}

public String getDate(){
    return date;
}

public void setDate(String date){
    this.date = date;
}

public String getDirection(){
    return direction;
}

public void setDirection(String direction){
    this.direction = direction;
}

public String getModel(){
    return model;
}

public void setModel(String model){
    this.model = model;
}

public String getAirlines(){
    return airlines;
}

public void setAirlines(String airlines){
    this.airlines = airlines;
}

public String getFrom(){
    return from;
}

public void setFrom(String from){
    this.from = from;
}

public String getTo(){
    return to;
}

public void setTo(String to){
    this.to = to;
}

}

最后我的活动。这就是我从数组中填充listview的方式，我喜欢类似于我的数据库。

import android.app.Activity;
import android.content.res.Resources;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class DatabaseCheck extends Activity {

    private ListView lvPlanes;
    private String[] planes;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_database_check);
        lvPlanes = (ListView) findViewById(R.id.list_all);
        initResources();
        initListView();
    }

    private void initResources() {
        Resources res = getResources();
        planes = res.getStringArray(R.array.listofplanes);
    }

    private void initListView() {
        lvPlanes.setAdapter(new ArrayAdapter<String>(
                getBaseContext(),
                android.R.layout.simple_list_item_1,
                planes));
    }
}

我知道我应该打开数据库，填充列表并关闭数据库。我知道我应该构建一个自定义适配器，但我不知道如何做我想要的。我尝试过做某事，但每次尝试都以app崩溃告终。谁能帮我？任何建议将不胜感激，谢谢你。

Answer 1

试试这个，定义一个 CursorAdapter ：

public class yourCursorAdapter extends CursorAdapter {
  public yourCursorAdapter(Context context, Cursor cursor) {
      super(context, cursor, 0);
  }

  @Override
  public View newView(Context context, Cursor cursor, ViewGroup parent) {
      return LayoutInflater.from(context).inflate(R.layout.item_todo, parent, false);
  }

  @Override
  public void bindView(View view, Context context, Cursor cursor) {

      // Find all fields to populate in inflated template
      // Example
      TextView tvDate = (TextView) view.findViewById(R.id.tvDate);

      // Extract all needed properties from cursor
      // Example
      String date = cursor.getString(cursor.getColumnIndexOrThrow("date"));

      // Populate all the required fields with extracted properties
      // Example
      tvDate.setText(date);

  }
}

然后，在initListView中将适配器设置为listview：

private void initListView() {
     DatabaseHelper handler = new DatabaseHelper(this);
     SQLiteDatabase db = handler.getWritableDatabase(); 
     Cursor cursor = db.rawQuery(YOUR_SQL_QUERY, null);  
     yourCursorAdapter adapter = new yourCursorAdapter(this, cursor);
     lvPlanes.setAdapter(adapter);
}

希望有所帮助

Android：从SQLite数据库填充ListView（多列）

1 个答案: