【IT168 技术文档】这个实例主要是对SDK中的Notepadv2Solution的修改和完善，因为本人在使用该sample发现一些错误和缺陷,主要是空指针异常。（1）Notepadv1.java：
package com.google.android.demo.notepad1;
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.Menu.Item;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class Notepadv1 extends ListActivity {
public static final int INSERT_ID = Menu.FIRST;
private static final int EXIT_ID = 0;
private static final int DELETE_ID = Menu.FIRST + 1;
private static final int ACTIVITY_EDIT = 1;
private static final int ACTIVITY_CREATE = 0;
private NotesDbAdapter mDbHelper;
private Cursor c;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.notepad_list);
mDbHelper = new NotesDbAdapter(this);
mDbHelper.open();
fillData();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
boolean result = super.onCreateOptionsMenu(menu);
menu.add(0, INSERT_ID, R.string.menu_insert);
menu.add(0, EXIT_ID, R.string.exit_notes);
menu.add(0, DELETE_ID, R.string.menu_delete);
return result;
}
@Override
public boolean onOptionsItemSelected(Item item) {
switch (item.getId()) {
case INSERT_ID:
createNote();
return true;
case EXIT_ID:
finish();
return true;
case DELETE_ID:
mDbHelper.deleteNote(getListView().getSelectedItemId());
fillData();
return true;
}
return super.onOptionsItemSelected(item);
}
private void createNote() {
Intent i = new Intent(this, NoteEdit.class);
startSubActivity(i, ACTIVITY_CREATE);
}
private void fillData() {
// Get all of the notes from the database and create the item list
c = mDbHelper.fetchAllNotes();
startManagingCursor(c);
String[] from = new String[] { NotesDbAdapter.KEY_TITLE };
int[] to = new int[] { R.id.text1 };
// Now create an array adapter and set it to display using our row
SimpleCursorAdapter notes =
new SimpleCursorAdapter(this, R.layout.notes_row, c, from, to);
setListAdapter(notes);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
c.moveTo(position);
Intent i = new Intent(this, NoteEdit.class);
i.putExtra(NotesDbAdapter.KEY_ROWID, id);
i.putExtra(NotesDbAdapter.KEY_TITLE, c.getString(
c.getColumnIndex(NotesDbAdapter.KEY_TITLE)));
i.putExtra(NotesDbAdapter.KEY_BODY, c.getString(
c.getColumnIndex(NotesDbAdapter.KEY_BODY)));
startSubActivity(i, ACTIVITY_EDIT);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, String data, Bundle extras) {
super.onActivityResult(requestCode, resultCode, data, extras);
switch(requestCode) {
case ACTIVITY_CREATE:
if(extras == null)
break;
String title = extras.getString(NotesDbAdapter.KEY_TITLE);
String body = extras.getString(NotesDbAdapter.KEY_BODY);
mDbHelper.createNote(title, body);
fillData();
break;
case ACTIVITY_EDIT:
if(extras == null)
break;
Long rowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
if (rowId != null) {
String editTitle = extras.getString(NotesDbAdapter.KEY_TITLE);
String editBody = extras.getString(NotesDbAdapter.KEY_BODY);
mDbHelper.updateNote(rowId, editTitle, editBody);
}
fillData();
break;
}
}
}
说明：
此activity主要是将为创建notepad做前期工作的，此外还做收尾工作，将从后台接受过来的数据显示出来。
图示：
（2）NoteEdit.java:
package com.google.android.demo.notepad1;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class NoteEdit extends Activity {
private EditText mTitleText;
private EditText mBodyText;
private Long mRowId;
@Override
protected void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.note_edit); mTitleText = (EditText) findViewById(R.id.title);
mBodyText = (EditText) findViewById(R.id.body);
Button confirmButton = (Button) findViewById(R.id.confirm);
mRowId = null;
Bundle extras = getIntent().getExtras();
if (extras != null) {
String title = extras.getString(NotesDbAdapter.KEY_TITLE);
String body = extras.getString(NotesDbAdapter.KEY_BODY);
mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
if (title != null) {
mTitleText.setText(title);
}
if (body != null) {
mBodyText.setText(body);
}
} confirmButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Bundle bundle = new Bundle();
bundle.putString(NotesDbAdapter.KEY_TITLE, mTitleText.getText().toString());
bundle.putString(NotesDbAdapter.KEY_BODY, mBodyText.getText().toString());
if (mRowId != null) {
bundle.putLong(NotesDbAdapter.KEY_ROWID, mRowId);
}
setResult(RESULT_OK, null, bundle);
finish();
}
});
}
}
说明：
接受前台的命令，开始创建notepad，并将数据传递到前台。注意if (extras != null) 可以可以防止输入数据为空时的空指针异常情况。
图示： （3）NotesDbAdapter.java:
package com.google.android.demo.notepad1;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import java.io.FileNotFoundException;
public class NotesDbAdapter {
public static final String KEY_TITLE="title";
public static final String KEY_BODY="body";
public static final String KEY_ROWID="_id";
private static final String DATABASE_CREATE =
"create table notes (_id integer primary key autoincrement, "
+ "title text not null, body 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 SQLiteDatabase mDb;
private final Context mCtx;
public NotesDbAdapter(Context ctx) {
this.mCtx = ctx;
}
public NotesDbAdapter open() throws SQLException {
try {
mDb = mCtx.openDatabase(DATABASE_NAME, null);
} catch (FileNotFoundException e) {
try {
mDb =
mCtx.createDatabase(DATABASE_NAME, DATABASE_VERSION, 0,
null);
mDb.execSQL(DATABASE_CREATE);
} catch (FileNotFoundException e1) {
throw new SQLException("Could not create database");
}
}
return this;
}
public void close() {
mDb.close();
}
public long createNote(String title, String body) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_TITLE, title);
initialValues.put(KEY_BODY, body);
return mDb.insert(DATABASE_TABLE, null, initialValues);
}
public boolean deleteNote(long rowId) {
return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
public Cursor fetchAllNotes() {
return mDb.query(DATABASE_TABLE, new String[] {
KEY_ROWID, KEY_TITLE, KEY_BODY}, null, null, null, null, null);
}
public Cursor fetchNote(long rowId) throws SQLException {
Cursor result = mDb.query(true, DATABASE_TABLE, new String[] {
KEY_ROWID, KEY_TITLE, KEY_BODY}, KEY_ROWID + "=" + rowId, null, null,
null, null);
if ((result.count() == 0) || !result.first()) {
throw new SQLException("No note matching ID: " + rowId);
}
return result;
}
public boolean updateNote(long rowId, String title, String body) {
ContentValues args = new ContentValues();
args.put(KEY_TITLE, title);
args.put(KEY_BODY, body);
return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}
说明：
数据库和数据库操作在里面。
(4)notepad_list.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<ListView android:id="@id/android:list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<TextView android:id="@id/android:empty"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/no_notes"/>
</LinearLayout>
(5)note_edi.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">
<LinearLayout android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/title" />
<EditText android:id="@+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"/>
</LinearLayout>
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/body" />
<EditText android:id="@+id/body"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:scrollbars="vertical" />
<Button android:id="@+id/confirm"
android:text="@string/confirm"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
(6)notes_row.xml:
<?xml version="1.0" encoding="utf-8"?>
<TextView android:id="@+id/text1"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
(7)strings.xml:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">Notepad v1</string>
<string name="no_notes">No Notes Yet</string>
<string name="menu_insert">Add Item</string>
<string name="exit_notes">Exit Notepad</string>
<string name="menu_delete">Delete Item</string>
<string name="title">Title</string>
<string name="body">Body</string>
<string name="confirm">Confirm</string>
<string name="edit_note">Edit Note</string>
</resources>
(8)AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.google.android.demo.notepad1">
<application android:icon="@drawable/icon">
<activity android:name=".Notepadv1" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".NoteEdit"></activity>
</application>
</manifest>
