java - 使用 Itext 以 PDF 格式显示来自 SQLite 数据库的结果

Question

我是编码世界的初学者，我正在尝试使用 IText 从我的应用程序生成 PDF。我设法创建了带有文本、表格等的基本 PDF。现在我想从已创建且不为空的数据库中检索数据。我查看了 StackOverflow 和 Internet 上的许多主题，但无法使其正常工作。

欢迎任何帮助

如果您还需要什么，请告诉我，在此先感谢您!

这是我的代码:

报告 Activity

public class ReportActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_report);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    //getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}

public void onClick_report(View view) {
    try {
        createPdf();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (DocumentException e) {
        e.printStackTrace();
    }

}

private void createPdf() throws FileNotFoundException, DocumentException {

    File pdfFolder = new File(getExternalFilesDir("report"), "report");
    Date date = new Date();
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(date);
    File myFile = new File(pdfFolder + timeStamp + ".pdf");
    OutputStream output = new FileOutputStream(myFile);

    DatabaseHandler db = new DatabaseHandler(getApplicationContext());
    Cursor cursor = db.getSepficItem();

    //Step 1
    Document document = new Document();

    //Step 2
    PdfWriter.getInstance(document, output);

    //Step 3
    document.open();

    //Step 4 Add content

    PdfPTable table = new PdfPTable(6);

    table.addCell("id col");
    table.addCell("day col");
    table.addCell("month col");
    table.addCell("Year col");
    table.addCell("type col");
    table.addCell("amount col");
    table.addCell("comment col");
    table.addCell("photo col");
    table.addCell("cust col");

    cursor.moveToFirst();
    int count = cursor.getCount();

    for (int j = 0; j < count; j++)
    {
        table.addCell(cursor.getString(cursor.getColumnIndex("id")));
        table.addCell(cursor.getString(cursor.getColumnIndex("day")));
        table.addCell(cursor.getString(cursor.getColumnIndex("month")));
        table.addCell(cursor.getString(cursor.getColumnIndex("year")));
        table.addCell(cursor.getString(cursor.getColumnIndex("type")));
        table.addCell(cursor.getString(cursor.getColumnIndex("amount")));
        table.addCell(cursor.getString(cursor.getColumnIndex("comment")));
        table.addCell(cursor.getString(cursor.getColumnIndex("photo")));
        table.addCell(cursor.getString(cursor.getColumnIndex("customername")));

        cursor.moveToNext();
    }

    //Step 5: Close the document
    document.close();
}

数据库助手:

public class DatabaseHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 18;
private static final String DATABASE_NAME = "ExpenseNote";

//Table Customer
private static final String TABLE_CUST = "Customer";
private static final String CUST_ID = "id";
private static final String CUST_NAME = "name";

//Table Expense
private static final String TABLE_EXPENSE = "Expense";
private static final String EXPENS_ID = "id";
private static final String EXPENS_DAY = "day";
private static final String EXPENS_MONTH = "month";
private static final String EXPENS_YEAR = "year";
private static final String EXPENS_TYPE = "type";
private static final String EXPENS_AMOUNT = "amount";
private static final String EXPENS_COMMENT = "comment";
private static final String EXPENS_PHOTO = "photo";
private static final String EXPENS_CUST = "customername";


public DatabaseHandler(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
    // Category table create query
    String CREATE_ITEM_TABLE = "CREATE TABLE IF NOT EXISTS "
            + TABLE_CUST + "("
            + CUST_ID + " integer primary key,"
            + CUST_NAME + " text not null)";
    db.execSQL(CREATE_ITEM_TABLE);

    String CREATE_EXPENSE_TABLE = "CREATE TABLE IF NOT EXISTS "
            + TABLE_EXPENSE + "("
            + EXPENS_ID + " integer PRIMARY KEY,"
            + EXPENS_DAY + " integer,"
            + EXPENS_MONTH + " integer,"
            + EXPENS_YEAR + " integer,"
            + EXPENS_TYPE + " text,"
            + EXPENS_AMOUNT + " real,"
            + EXPENS_COMMENT + " text,"
            + EXPENS_PHOTO + " text,"
            + EXPENS_CUST + " text)";
    // + " FOREIGN KEY (" + CUST_ID + ") REFERENCES " + TABLE_CUST + "(" + CUST_ID + "));";
    db.execSQL(CREATE_EXPENSE_TABLE);

}


public  Cursor getSepficItem(){
    // Select All Query
    SQLiteDatabase db = this.getReadableDatabase();
    String q = "SELECT * FROM Expense";
    Cursor mCursor = db.rawQuery(q, null);
    // closing connection
    mCursor.close();
    db.close();

    // returning customer
    return mCursor;
}

日志:

FATAL EXCEPTION: main java.lang.IllegalStateException: Could not execute method for android:onClick
      at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
      at android.view.View.performClick(View.java:5610)
      at android.view.View$PerformClick.run(View.java:22265)
      at android.os.Handler.handleCallback(Handler.java:751)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:154)
      at android.app.ActivityThread.main(ActivityThread.java:6077)
      at java.lang.reflect.Method.invoke(Native Method)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
   Caused by: java.lang.reflect.InvocationTargetException
      at java.lang.reflect.Method.invoke(Native Method)
      at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
      at android.view.View.performClick(View.java:5610) 
      at android.view.View$PerformClick.run(View.java:22265) 
      at android.os.Handler.handleCallback(Handler.java:751) 
      at android.os.Handler.dispatchMessage(Handler.java:95) 
      at android.os.Looper.loop(Looper.java:154) 
      at android.app.ActivityThread.main(ActivityThread.java:6077) 
      at java.lang.reflect.Method.invoke(Native Method) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756) 
   Caused by: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteQuery: SELECT * FROM Expense
      at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
      at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:58)
      at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:143)
      at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:132)
      at android.database.AbstractCursor.moveToPosition(AbstractCursor.java:219)
      at android.database.AbstractCursor.moveToFirst(AbstractCursor.java:258)
      at lu.digitalsecurity.expensenote.ReportActivity.createPdf(ReportActivity.java:89)
      at lu.digitalsecurity.expensenote.ReportActivity.onClick_report(ReportActivity.java:35)
      at java.lang.reflect.Method.invoke(Native Method) 
      at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
      at android.view.View.performClick(View.java:5610) 
      at android.view.View$PerformClick.run(View.java:22265) 
      at android.os.Handler.handleCallback(Handler.java:751) 
      at android.os.Handler.dispatchMessage(Handler.java:95) 
      at android.os.Looper.loop(Looper.java:154) 
      at android.app.ActivityThread.main(ActivityThread.java:6077) 
      at java.lang.reflect.Method.invoke(Native Method) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756) 

按要求编辑:

XML文件(目前只有一个简单的按钮):

<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"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".ReportActivity"
tools:showIn="@layout/activity_report">
<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button"
    app:layout_constraintTop_toTopOf="parent"
    android:layout_marginTop="45dp"
    android:layout_marginLeft="50dp"
    app:layout_constraintLeft_toLeftOf="parent"
    android:layout_marginRight="50dp"
    app:layout_constraintRight_toRightOf="parent"
    android:onClick="onClick_report"/>

Answer 1

实际上堆栈会告诉您错误在哪里:“attempt to re-open an already-closed object”。

当你做 mCursor.close() 基本上你说系统“我不会再使用它了，你可以释放相关资源”。

恕我直言，你应该有一个 Expense 类，看起来像:

public class Expense {
    private int id, day, month, year;
    private String type;
    // and so on...
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
    // Other getters/setters

}

你的方法 getSepficItem() 应该返回一个列表:

public List<Expense> getSepficItem() {
    List<Expense> result = new ArrayList();
    // Select All Query
    SQLiteDatabase db = this.getReadableDatabase();
    String q = "SELECT * FROM Expense";
    Cursor mCursor = db.rawQuery(q, null);
    if (cursor.moveToFirst()) {
        do {
            Expense expense = new Expense();
            expense.setId(Integer.parseInt(cursor.getString(0)));
            // etc...
            expense.setType(cursor.getString(2));
            // etc...
            result.add(contact);
        } while (cursor.moveToNext());
    }
    mCursor.close();
    db.close();
    return result;
}

生成 PDF 的方法应该使用 Expense，而不是 cursor。

请注意，这不是您特定问题的完整解决方案，而是有关如何组织代码的线索。

最后适配pdf创建:

createPdf() {

  for (Expense expense : db.getSepficItem()) {
    // ..
    table.addCell(expense.getId());
  }
}