android - 如何将sqlite中的数据显示到listview android studio

Question

我需要有关在本地数据库 SQLite 的 ListView 中显示数据的帮助。我已经在数据库中有数据。 所以请帮我看看我在哪里做错了？

DatabseHelper.Java代码如下

private static final String DATABASE_NAME = "Barcode_Printing.db";
static final String TABLE_NAME = "Item_Master";
static final String Item_name = "Item_Name";
static final String wEight = "Weight";
static final String MrP = "MRP";
static final String BarcodE = "BARCODE";

public DatabaseHelper(Context context)
{
    super(context, DATABASE_NAME, null, 1);
    SQLiteDatabase db = this.getReadableDatabase();
}

@Override
public void onCreate(SQLiteDatabase db)
{
    db.execSQL("CREATE TABLE " + TABLE_NAME + " (" + BarcodE + " INTEGER PRIMARY KEY, " + Item_name + " TEXT, " + wEight + " TEXT, " + MrP + " INTEGER, EXPIRY_DATE TEXT)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1)
{
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}

public Cursor getAllItems() {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.query(TABLE_NAME, new String[]{BarcodE, Item_name, wEight, MrP},
            null, null, null, null, null);
    if (cursor != null) {
        cursor.moveToFirst();
        return cursor;
    }
    else
    {
        return null;
    }
}

下面是 activity_dispaly_items.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.packlab.alpesh.barcodeprinting.Display_Items">

<android.support.design.widget.AppBarLayout
    android:id="@+id/appBarLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/AppTheme.AppBarOverlay">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:popupTheme="@style/AppTheme.PopupOverlay" />

</android.support.design.widget.AppBarLayout>

<ListView
    android:id="@+id/lvItem_Display"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginTop="80dp"
    tools:layout_editor_absoluteY="3dp" />

</android.support.design.widget.CoordinatorLayout>

下面是 items_display_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">

<TextView
    android:id="@+id/tvItemName"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="16dp"
    android:text="TextView"
    android:textSize="18sp"
    android:textStyle="bold"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.065"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<TextView
    android:id="@+id/tvBarcode"
    android:layout_width="wrap_content"
    android:layout_height="19dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="48dp"
    android:text="TextView"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.119"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<TextView
    android:id="@+id/tvMrp"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:text="TextView"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.119"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/tvWeight" />

<TextView
    android:id="@+id/tvWeight"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:text="TextView"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.119"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/tvBarcode" />

  </android.support.constraint.ConstraintLayout>

DisplayItems.Java 代码下方

它直接给我错误“有一个错误!” 它不要尝试。它直接进入 Catch。

public class Display_Items extends AppCompatActivity
{
SimpleCursorAdapter simpleCursorAdapter;
ListView display_Items;

DatabaseHelper DatabaseHelper;

protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_display__items);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    spinner = findViewById(R.id.spinner_Comapny);
    setSupportActionBar(toolbar);

    display_Items = findViewById(R.id.lvItem_Display);
    DatabaseHelper = new DatabaseHelper(this);

    loadSpinnerData();
    displayProductList();
}

private void displayProductList() 
{
    try
    {
        Cursor cursor = DatabaseHelper.getAllItems();
        if (cursor == null)
        {
            Toast.makeText(Display_Items.this, "Unable to generate cursor.", Toast.LENGTH_SHORT).show();
            return;
        }
        if (cursor.getCount() == 0)
        {
            Toast.makeText(Display_Items.this, "No Products in the Database.", Toast.LENGTH_SHORT).show();
            return;
        }
        String[] columns = new String[] {
                DatabaseHelper.BarcodE,
                DatabaseHelper.Item_name,
                DatabaseHelper.wEight,
                DatabaseHelper.MrP
        };
        int[] boundTo = new int[] {
                R.id.tvBarcode,
                R.id.tvItemName,
                R.id.tvWeight,
                R.id.tvMrp
        };
        simpleCursorAdapter = new SimpleCursorAdapter(this,
                R.layout.item_display_layout,
                cursor,
                columns,
                boundTo,
                0);
        display_Items.setAdapter(simpleCursorAdapter);
    }
    catch (Exception ex)
    {
        Toast.makeText(Display_Items.this, "There was an error!", Toast.LENGTH_SHORT).show();
    }
}
}

Answer 1

我提供了从代码下方使用的 sqllite 读取数据的简单方法..

先做一个pojo类..

public class MyTable {
public String itemName,weight,mrp,barcod;

然后在数据基类make方法之后读取数据...

    public List<MyTable> getMyItems() {
    List<MyTable> mySuperList = new ArrayList<>();
    SQLiteDatabase db = this.getReadableDatabase();
    String selectQuery = "SELECT  * FROM " + TABLE_NAME ;
    Cursor c = db.rawQuery(selectQuery, null);
    if (c != null) {
        c.moveToFirst();
        while (c.isAfterLast() == false) {
            MyTable myTable = new MyTable();
            myTable.itemName = (c.getString(c.getColumnIndex("Item_Name")));
            myTable.weight = (c.getString(c.getColumnIndex("Weight")));
            myTable.mrp = (c.getString(c.getColumnIndex("MRP")));
            myTable.barcod = (c.getString(c.getColumnIndex("BARCODE")));

            mySuperList.add(myTable);
            c.moveToNext();
        }
    }
    return mySuperList;
}

然后在使用了这个方法之后，将数据绑定(bind)到listview中。