Question

我想首先要求您的集体耐心......我正在尝试通过Google示例代码的试错类型修改来学习Android程序：“记事本教程”到目前为止，事情已经非常慢慢来。（我也在阅读Head First Java :)。

我的目标是在教程应用程序中添加一个额外的TextEdit字段和一个Button ...我希望用户能够在该字段中输入文本，然后按下按钮并将他们刚刚输入的文本附加到数据库然后下拉到scrollView中的textView，以便查看器可以看到条目的记录。基本上，我的目标是允许用户将无限数量的数据（取决于单击按钮的次数）添加到每个数据库条目中。我已经获得了部分方式（添加一个新的db字段，创建TextEdit和按钮等...）但我无法将它们放在一起...具体如何使它在db端工作。我不确定我是否正确地解释了这一点......但我会附上相关的源代码以试图让它更清楚。

（注意：KEY_HOUSE是我添加的db字段，house / mHouseText是相关的相关变量）

NoteEdit.java

    package com.android.demo.notepad3;


import android.R.string;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;
import android.widget.TableRow.LayoutParams;

public class NoteEdit extends Activity{

    private EditText mTitleText;
    private EditText mBodyText;
    private Long mRowId;
    private NotesDbAdapter mDbHelper;
    Button btn;
    int counter = 0;
    private EditText mHouseText;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mDbHelper = new NotesDbAdapter(this);
        mDbHelper.open();

        setContentView(R.layout.note_edit);
        setTitle(R.string.edit_note);

        mTitleText = (EditText) findViewById(R.id.title);
        mBodyText = (EditText) findViewById(R.id.body);
        mHouseText = (EditText) findViewById(R.id.house);

        Button confirmButton = (Button) findViewById(R.id.confirm);
        Button btn = (Button) findViewById(R.id.Button01);


        mRowId = (savedInstanceState == null) ? null :
            (Long) savedInstanceState.getSerializable(NotesDbAdapter.KEY_ROWID);
        if (mRowId == null) {
            Bundle extras = getIntent().getExtras();
            mRowId = extras != null ? extras.getLong(NotesDbAdapter.KEY_ROWID)
                                    : null;
        }

        populateFields();


        confirmButton.setOnClickListener(new View.OnClickListener() {

            public void onClick(View view) {
                setResult(RESULT_OK);
                finish();
            }

        });



    btn.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            addrow();

        }

    });

    }



    private void populateFields() {
        if (mRowId != null) {
            Cursor note = mDbHelper.fetchNote(mRowId);
            startManagingCursor(note);
            mTitleText.setText(note.getString(
                    note.getColumnIndexOrThrow(NotesDbAdapter.KEY_TITLE)));
            mBodyText.setText(note.getString(
                    note.getColumnIndexOrThrow(NotesDbAdapter.KEY_BODY)));
            mHouseText.setText(note.getString(
                    note.getColumnIndexOrThrow(NotesDbAdapter.KEY_HOUSE)));
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        saveState();
        outState.putSerializable(NotesDbAdapter.KEY_ROWID, mRowId);
    }

    @Override
    protected void onPause() {
        super.onPause();
        saveState();
    }

    @Override
    protected void onResume() {
        super.onResume();
        populateFields();
    }

    private void saveState() {
        String title = mTitleText.getText().toString();
        String body = mBodyText.getText().toString();
        String house = mHouseText.getText().toString();

        if (mRowId == null) {
            long id = mDbHelper.createNote(title, body, house);
            if (id > 0) {
                mRowId = id;
            }
        } else {
            mDbHelper.updateNote(mRowId, title, body, house);
        }
    }


    private void addrow(){

        //mHouseText = (EditText) findViewById(R.id.house);
        String house = mHouseText.getText().toString();
        // get a reference for the TableLayout
                TableLayout table = (TableLayout) findViewById(R.id.TableLayout02);

        // create a new TableRow
        TableRow row = new TableRow(this);



        // create a new TextView
        TextView t = new TextView(this);
        // set the text to "text xx"
        t.setText(house);

        // create a CheckBox
        CheckBox c = new CheckBox(this);

        // add the TextView and the CheckBox to the new TableRow
        row.addView(t);
        row.addView(c);

        // add the TableRow to the TableLayout
        table.addView(row,new TableLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));


    }


}

NotesDbAdapter.java

package com.android.demo.notepad3;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;


 * Simple notes database access helper class. Defines the basic CRUD operations
 * for the notepad example, and gives the ability to list all notes as well as
 * retrieve or modify a specific note.
 * 
 * This has been improved from the first version of this tutorial through the
 * addition of better error handling and also using returning a Cursor instead
 * of using a collection of inner classes (which is less scalable and not
 * recommended).

public class NotesDbAdapter {

    public static final String KEY_TITLE = "title";
    public static final String KEY_BODY = "body";
    public static final String KEY_HOUSE = "house";
    public static final String KEY_ROWID = "_id";

    private static final String TAG = "NotesDbAdapter";
    private DatabaseHelper mDbHelper;
    private SQLiteDatabase mDb;

    /**
     * Database creation sql statement
     */
    private static final String DATABASE_CREATE =
        "create table notes (_id integer primary key autoincrement, "
        + "title text not null, body text not null, house text not null);";

    private static final String DATABASE_NAME = "data";
    private static final String DATABASE_TABLE = "notes";
    private static final int DATABASE_VERSION = 2;

    private final Context mCtx;

    private static class DatabaseHelper extends SQLiteOpenHelper {

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

        @Override
        public void onCreate(SQLiteDatabase db) {

            db.execSQL(DATABASE_CREATE);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS notes");
            onCreate(db);
        }
    }

    /**
     * Constructor - takes the context to allow the database to be
     * opened/created
     * 
     * @param ctx the Context within which to work
     */
    public NotesDbAdapter(Context ctx) {
        this.mCtx = ctx;
    }

    /**
     * Open the notes database. If it cannot be opened, try to create a new
     * instance of the database. If it cannot be created, throw an exception to
     * signal the failure
     * 
     * @return this (self reference, allowing this to be chained in an
     *         initialization call)
     * @throws SQLException if the database could be neither opened or created
     */
    public NotesDbAdapter open() throws SQLException {
        mDbHelper = new DatabaseHelper(mCtx);
        mDb = mDbHelper.getWritableDatabase();
        return this;
    }

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


    /**
     * Create a new note using the title and body provided. If the note is
     * successfully created return the new rowId for that note, otherwise return
     * a -1 to indicate failure.
     * 
     * @param title the title of the note
     * @param body the body of the note
     * @return rowId or -1 if failed
     */
    public long createNote(String title, String body, String house) {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_TITLE, title);
        initialValues.put(KEY_BODY, body);
        initialValues.put(KEY_HOUSE, house);

        return mDb.insert(DATABASE_TABLE, null, initialValues);
    }

    /**
     * Delete the note with the given rowId
     * 
     * @param rowId id of note to delete
     * @return true if deleted, false otherwise
     */
    public boolean deleteNote(long rowId) {

        return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
    }

    /**
     * Return a Cursor over the list of all notes in the database
     * 
     * @return Cursor over all notes
     */
    public Cursor fetchAllNotes() {

        return mDb.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_TITLE,
                KEY_BODY, KEY_HOUSE}, null, null, null, null, null);
    }

    /**
     * Return a Cursor positioned at the note that matches the given rowId
     * 
     * @param rowId id of note to retrieve
     * @return Cursor positioned to matching note, if found
     * @throws SQLException if note could not be found/retrieved
     */
    public Cursor fetchNote(long rowId) throws SQLException {

        Cursor mCursor =

            mDb.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
                    KEY_TITLE, KEY_BODY, KEY_HOUSE}, KEY_ROWID + "=" + rowId, null,
                    null, null, null, null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;

    }

    /**
     * Update the note using the details provided. The note to be updated is
     * specified using the rowId, and it is altered to use the title and body
     * values passed in
     * 
     * @param rowId id of note to update
     * @param title value to set note title to
     * @param body value to set note body to
     * @return true if the note was successfully updated, false otherwise
     */
    public boolean updateNote(long rowId, String title, String body, String house) {
        ContentValues args = new ContentValues();
        args.put(KEY_TITLE, title);
        args.put(KEY_BODY, body);
        args.put(KEY_HOUSE, house);

        return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
    }
}

NoteEdit.xml

 <?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <TableLayout android:id="@+id/TableLayout01" android:layout_width="fill_parent" android:layout_height="wrap_content"  android:stretchColumns="0">

  <TableRow android:id="@+id/TableRow01" android:layout_width="wrap_content" android:layout_height="wrap_content">

        <TextView android:layout_width="fill_parent"
            android:layout_height="wrap_content" 
            android:text="@string/title" />
        <EditText android:id="@+id/title" 
          android:layout_height="wrap_content" 
            android:layout_width="wrap_content" android:hint="Montague St."/>
  </TableRow>

  <TableRow android:id="@+id/TableRow02" android:layout_width="wrap_content" android:layout_height="wrap_content">

        <TextView android:layout_width="wrap_content"
            android:layout_height="wrap_content" 
            android:text="@string/body" />
        <EditText android:id="@+id/body" android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:scrollbars="vertical" android:hint="44"/>
        </TableRow>


    </TableLayout>

<ScrollView android:id="@+id/ScrollView01" android:layout_width="wrap_content" android:layout_height="wrap_content">

  <TableLayout android:id="@+id/TableLayout02" android:layout_width="fill_parent" android:layout_height="wrap_content" android:stretchColumns="0">

    <TableRow android:id="@+id/TableRow03" android:layout_width="wrap_content" android:layout_height="wrap_content">
      <EditText android:id="@+id/house" android:layout_width="fill_parent" android:layout_height="wrap_content" android:hint="House Number"></EditText>

      <CheckBox android:id="@+id/CheckBox01" android:layout_width="wrap_content" android:layout_height="wrap_content"></CheckBox>
    </TableRow>
    <Button android:id="@+id/Button01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Add House"></Button>

  </TableLayout>
</ScrollView>

    <LinearLayout android:orientation="horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
    <Button android:id="@+id/confirm" 
      android:text="@string/confirm"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>
</LinearLayout>

我认识到我的问题是非常开放的，“n00b” - 但是，任何帮助，甚至只是在正确的方向上轻推，都会非常感激。

由于

谢

Answer 1

在数据库类中创建一个允许您更新记录的方法。然后在按钮上的onClickListener中调用该方法，该按钮将读取值并将其传递给数据库方法以进行更新。这不会是完美的，但应该有效。

Answer 2

听起来你想要的是数据中的一对多关系。为此，你要创建另一个像“note_houses”的表，其中每个记录是一个单独的文本条目/“house”，其中note_id列充当外键，如下所示：

create table note_houses (
    _id integer primary key autoincrement,
    note_id integer not null references notes (_id),
    entry text not null
)

当有人点击按钮添加新条目时，它应该在此表中插入一条新记录（为此，您必须编写类似于createNote的createHouse方法）。然后可以使用ListView生成下面出现的滚动条目列表。需要从DbAdapter中的fetchHousesByNote方法生成ListView适配器的Cursor，该方法将执行如下查询：

select * from note_houses where note_id=?

...然后将note_id参数绑定到正在编辑的音符的ID。

这有意义吗？这是你要求的吗？

关于在Android中扩展Notepad教程的一个非常开放的，n00b式的问题

2 个答案: