如何将微调器项目与数据连接起来

Question

我正在尝试为汽车服务构建 Android 应用。我放了一个带有“换油”等项目的微调器。是否可以进行这种活动，当我从微调器中选择一些东西时，应用程序会显示距离下一次更换机油还有多少公里和时间？我应该将 SQLite 与 int 和 time 一起使用吗？

Answer 1

当然可以。使用setOnItemClickListener() 设置监听器并触发您喜欢的任何代码。

Answer 2

这是一个使用微调器的示例，选择它会显示到下一项更改的距离和当前里程表读数。这是非常基本的，而不是使用服务日期/时间使用里程表读数和（公里）。

我应该使用带有 int 和 time 的 SQLite 吗？

• 您可能希望距离和时间两个间隔，因为维修通常以先到者为准（行驶距离或自上次维修以来的时间）示例仅假定距离。。李>

它基于 3 个表，一张用于 汽车，一张用于 service_items（机油滤清器更换等），然后是映射/参考表（间隔）。这对于每个汽车/服务项目都有一行，每行包括引用的汽车和引用的 service_item、上次维修该项目时的里程表读数和维修间隔。

它有一个微调器，可让您选择服务项目，选择服务项目会显示该项目的下一个服务需要多长时间。

数据库助手，DBHelper.java（SQLiteOpenHelper 类的子类）是：-

public class DBHelper extends SQLiteOpenHelper {

    public static final String DBNAME = "service";
    public static final int DBVERSION = 1;
    public static final String TBITEM = "service_item";
    public static final String TBCAR = "car";
    public static final String TBINTERVAL = "interval";

    public static final String COL_TBITEMS_ID = BaseColumns._ID;
    public static final String COL_TBITEMS_NAME = "item_name";
    static final String crt_items_sql = "CREATE TABLE IF NOT EXISTS " +
            TBITEM + "(" +
            COL_TBITEMS_ID + " INTEGER PRIMARY KEY, " +
            COL_TBITEMS_NAME + " TEXT " +
            ")";

    public static final String COL_TBCAR_ID = BaseColumns._ID;
    public static final String COL_TBCAR_OWNERNAME = "owner_name";
    public static final String COL_TBCAR_ODOMETER = "odometer";
    static final String crt_car_sql = "CREATE TABLE IF NOT EXISTS " +
            TBCAR + "(" +
            COL_TBCAR_ID + " INTEGER PRIMARY KEY, " +
            COL_TBCAR_OWNERNAME + " TEXT, " +
            COL_TBCAR_ODOMETER + " INTEGER " +
            ")";

    public static final String COL_TBINTERVAL_ITEMREF = "item_id_reference";
    public static final String COL_TBINTERVAL_CARREF = "car_id_reference";
    public static final String COL_TBINTERVAL_INTERVAL = "item_interval";
    public static final String COL_TBINTERVAL_LASTDONE = "item_last_done";
    static final String crt_intervals_sql = "CREATE TABLE IF NOT EXISTS " +
            TBINTERVAL + "(" +
            COL_TBINTERVAL_ITEMREF + " INTEGER REFERENCES " + TBITEM + "(" + COL_TBITEMS_ID + ")," +
            COL_TBINTERVAL_CARREF + " INTEGER REFERENCES " + TBCAR + "(" + COL_TBCAR_ID + ")," +
            COL_TBINTERVAL_INTERVAL + " INTEGER, " +
            COL_TBINTERVAL_LASTDONE + " INTEGER DEFAULT 0 " +
            ")";

    SQLiteDatabase mDB;

    public DBHelper(Context context) {
        super(context, DBNAME, null, DBVERSION);
        mDB = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(crt_items_sql);
        db.execSQL(crt_car_sql);
        db.execSQL(crt_intervals_sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i1) {

    }

    public long addCar(String name, long odometer) {
        ContentValues cv = new ContentValues();
        cv.put(COL_TBCAR_OWNERNAME,name);
        cv.put(COL_TBCAR_ODOMETER,odometer);
        return mDB.insert(TBCAR,null,cv);
    }

    public long addItem(String name) {
        ContentValues cv = new ContentValues();
        cv.put(COL_TBITEMS_NAME,name);
        return mDB.insert(TBITEM,null,cv);
    }

    public long addInterval(long item_id, long car_id, long interval, long last_done) {
        ContentValues cv = new ContentValues();
        cv.put(COL_TBINTERVAL_ITEMREF, item_id);
        cv.put(COL_TBINTERVAL_CARREF, car_id);
        cv.put(COL_TBINTERVAL_INTERVAL,interval);
        cv.put(COL_TBINTERVAL_LASTDONE,last_done);
        return mDB.insert(TBINTERVAL,null,cv);
    }


    public long getCarOdometer(long car_id) {
        long rv = -1;
        Cursor csr = mDB.query(TBCAR,null,null,null,null,null,null);
        if (csr.moveToFirst()) {
            rv = csr.getLong(csr.getColumnIndex(COL_TBCAR_ODOMETER));
        }
        csr.close();
        return rv;
    }

    public long getNextDueForItem(long car_id, long item_id) {
        long rv = -1;
        long odometer = getCarOdometer(car_id);
        long last_done = 0;
        long interval = 0;
        String whereclause = COL_TBINTERVAL_ITEMREF + "=? AND " + COL_TBINTERVAL_CARREF + "=?";
        String[] whereargs = new String[]{String.valueOf(item_id),String.valueOf(car_id)};
        Cursor csr = mDB.query(TBINTERVAL,null,whereclause,whereargs,null,null,null);
        if (csr.moveToFirst()) {
            last_done = csr.getLong(csr.getColumnIndex(COL_TBINTERVAL_LASTDONE));
            interval = csr.getLong(csr.getColumnIndex(COL_TBINTERVAL_INTERVAL));
            long dueat = last_done + interval;
            rv = dueat - odometer;
        }
        csr.close();
        return rv;
    }
}

Activity MainActivity.java 是：-

public class MainActivity extends AppCompatActivity {

    Spinner mSpinner;
    TextView mSpinner_selection;
    ArrayAdapter<String> mSA;
    ArrayList<String> items = new ArrayList<>(
            Arrays.asList("Change Oil","Change Oil Filter","Change Air Filter","Change Spark Plugs")
    );
    DBHelper mDBHlpr;
    long mCurrentCar = 1;

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

        mSpinner = this.findViewById(R.id.spinner);
        mSpinner_selection = this.findViewById(R.id.selected_spinner);
        mSpinner_selection.setText("Nothing selected as yet"); //<<<< will likely not be seen

        // Instaiate the Database Helper (will create the Database and tables when first run)
        mDBHlpr = new DBHelper(this);
        addSomeData();
        handleSpinner();
    }

    // Setup the Spinner and the Item Select Listener
    private void handleSpinner() {
        if (mSA == null) {
            mSA = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,items);
            mSpinner.setAdapter(mSA);
            mSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    //<<<<<<<<<< NOTE not the best way as assumes a direct map
                    // from the list to the service_item.
                    long duein = mDBHlpr.getNextDueForItem(mCurrentCar,(long)i + 1);
                    long odometer = mDBHlpr.getCarOdometer(mCurrentCar);
                    String text_to_show =
                            "You are due to " + mSA.getItem(i) + " in " + String.valueOf(duein) +
                                    "Your Odometer reads " + String.valueOf(odometer);
                    mSpinner_selection.setText(text_to_show);
                }
                @Override
                public void onNothingSelected(AdapterView<?> adapterView) {
                }
            });
        }
    }

    // Add some data, a car and the service items based upon the ArrayList of items
    // noting that for display purposes the interval increase per service_item
    private void addSomeData() {
        long thiscar = mDBHlpr.addCar("My Car",1123);
        long interval = 10000;
        for (String s: items) {
            long thisitem = mDBHlpr.addItem(s);
            mDBHlpr.addInterval(thisitem,thiscar,interval,0);
            interval = interval + 500;
        }
    }
}

MainActivity 的布局是 activity_main.xml 是：-

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
    </Spinner>

    <TextView
        android:id="@+id/selected_spinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

• 注意这只是一个演示，展示如何使用微调器。
• 首次运行时会显示：-

• 选择更换机油滤清器将显示：-

• 10500，因为在 MainActivity 的 addSomeData 方法中，500 逐渐添加到服务区间（只是为了显示不同的数据）。