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我想首先请求你们的耐心等待...我正在尝试通过 Google 示例代码的试错类型修改来学习 Android 编程:“记事本教程”到目前为止，一切都非常顺利进展缓慢。 (我也在读 Head First Java :)
我的目标是向教程应用程序添加一个额外的 TextEdit 字段和一个按钮...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，以便查看者可以看到条目的记录。基本上，我的目标是允许用户将不定数量的数据(取决于单击按钮的次数)添加到每个数据库条目中。我已经完成了部分工作(添加新的数据库字段、创建 TextEdit 和按钮等)，但我无法将它们放在一起……特别是如何使其在数据库端工作。我不确定我是否正确解释了这一点......但我会附上相关的源代码以尽量使其更清楚。
(注意:KEY_HOUSE是我添加的db字段，house/mHouseText是相关变量)
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>
我知道我的问题是非常开放的，并且是“n00b”式的，但是任何帮助，甚至只是朝着正确方向的插入，都将不胜感激。
谢谢
弗兰克