The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
/*
* Copyright (C) 2007 The Android开源工程
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.notepad;
import android.app.Activity;
import android.content.ClipData;
import android.content.ClipboardManager;
import android.content.ComponentName;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.content.res.Resources;
import android.database.Cursor;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.net.Uri;
import android.os.Bundle;
import android.util.AttributeSet;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.EditText;
/**
* This Activity handles "editing" a note, where editing is responding to
* {@link Intent#ACTION_VIEW} (request to view data), edit a note
* {@link Intent#ACTION_EDIT}, create a note {@link Intent#ACTION_INSERT}, or
* create a new note from the current contents of the clipboard {@link Intent#ACTION_PASTE}.
*
* NOTE: Notice that the provider operations in this Activity are taking place on the UI thread.
* This is not a good practice. It is only done here to make the code more readable. A real
* application should use the {@link android.content.AsyncQueryHandler}
* or {@link android.os.AsyncTask} object to perform operations asynchronously on a separate thread.
*/
public class NoteEditor extends Activity {
// For logging and debugging purposes
private static final String TAG = "NoteEditor";
/*
* Creates a projection that returns the note ID and the note contents.
*/
private static final String[] PROJECTION =
new String[] {
NotePad.Notes._ID,
NotePad.Notes.COLUMN_NAME_TITLE,
NotePad.Notes.COLUMN_NAME_NOTE
};
// A label for the saved state of the activity
private static final String ORIGINAL_CONTENT = "origContent";
// This Activity can be started by more than one action. Each action is represented
// as a "state" constant
private static final int STATE_EDIT = 0;
private static final int STATE_INSERT = 1;
// Global mutable variables
private int mState;
private Uri mUri;
private Cursor mCursor;
private EditText mText;
private String mOriginalContent;
/**
* Defines a custom EditText View that draws lines between each line of text that is displayed.
*/
public static class LinedEditText extends EditText {
private Rect mRect;
private Paint mPaint;
// This constructor is used by LayoutInflater
public LinedEditText(Context context, AttributeSet attrs) {
super(context, attrs);
// Creates a Rect and a Paint object, and sets the style and color of the Paint object.
mRect = new Rect();
mPaint = new Paint();
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setColor(0x800000FF);
}
/**
* This is called to draw the LinedEditText object
* @param canvas The canvas on which the background is drawn.
*/
@Override
protected void onDraw(Canvas canvas) {
// Gets the number of lines of text in the View.
int count = getLineCount();
// Gets the global Rect and Paint objects
Rect r = mRect;
Paint paint = mPaint;
/*
* Draws one line in the rectangle for every line of text in the EditText
*/
for (int i = 0; i < count; i++) {
// Gets the baseline coordinates for the current line of text
int baseline = getLineBounds(i, r);
/*
* Draws a line in the background from the left of the rectangle to the right,
* at a vertical position one dip below the baseline, using the "paint" object
* for details.
*/
canvas.drawLine(r.left, baseline + 1, r.right, baseline + 1, paint);
}
// Finishes up by calling the parent method
super.onDraw(canvas);
}
}
/**
* This method is called by Android when the Activity is first started. From the incoming
* Intent, it determines what kind of editing is desired, and then does it.
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/*
* Creates an Intent to use when the Activity object's result is sent back to the
* caller.
*/
final Intent intent = getIntent();
/*
* Sets up for the edit, based on the action specified for the incoming Intent.
*/
// Gets the action that triggered the intent filter for this Activity
final String action = intent.getAction();
// For an edit action:
if (Intent.ACTION_EDIT.equals(action)) {
// Sets the Activity state to EDIT, and gets the URI for the data to be edited.
mState = STATE_EDIT;
mUri = intent.getData();
// For an insert or paste action:
} else if (Intent.ACTION_INSERT.equals(action)
|| Intent.ACTION_PASTE.equals(action)) {
// Sets the Activity state to INSERT, gets the general note URI, and inserts an
// empty record in the provider
mState = STATE_INSERT;
mUri = getContentResolver().insert(intent.getData(), null);
/*
* If the attempt to insert the new note fails, shuts down this Activity. The
* originating Activity receives back RESULT_CANCELED if it requested a result.
* Logs that the insert failed.
*/
if (mUri == null) {
// Writes the log identifier, a message, and the URI that failed.
Log.e(TAG, "Failed to insert new note into " + getIntent().getData());
// Closes the activity.
finish();
return;
}
// Since the new entry was created, this sets the result to be returned
// set the result to be returned.
setResult(RESULT_OK, (new Intent()).setAction(mUri.toString()));
// If the action was other than EDIT or INSERT:
} else {
// Logs an error that the action was not understood, finishes the Activity, and
// returns RESULT_CANCELED to an originating Activity.
Log.e(TAG, "Unknown action, exiting");
finish();
return;
}
/*
* Using the URI passed in with the triggering Intent, gets the note or notes in
* the provider.
* Note: This is being done on the UI thread. It will block the thread until the query
* completes. In a sample app, going against a simple provider based on a local database,
* the block will be momentary, but in a real app you should use
* android.content.AsyncQueryHandler or android.os.AsyncTask.
*/
mCursor = managedQuery(
mUri, // The URI that gets multiple notes from the provider.
PROJECTION, // A projection that returns the note ID and note content for each note.
null, // No "where" clause selection criteria.
null, // No "where" clause selection values.
null // Use the default sort order (modification date, descending)
);
// For a paste, initializes the data from clipboard.
// (Must be done after mCursor is initialized.)
if (Intent.ACTION_PASTE.equals(action)) {
// Does the paste
performPaste();
// Switches the state to EDIT so the title can be modified.
mState = STATE_EDIT;
}
// Sets the layout for this Activity. See res/layout/note_editor.xml
setContentView(R.layout.note_editor);
// Gets a handle to the EditText in the the layout.
mText = (EditText) findViewById(R.id.note);
/*
* If this Activity had stopped previously, its state was written the ORIGINAL_CONTENT
* location in the saved Instance state. This gets the state.
*/
if (savedInstanceState != null) {
mOriginalContent = savedInstanceState.getString(ORIGINAL_CONTENT);
}
}
/**
* This method is called when the Activity is about to come to the foreground. This happens
* when the Activity comes to the top of the task stack, OR when it is first starting.
*
* Moves to the first note in the list, sets an appropriate title for the action chosen by
* the user, puts the note contents into the TextView, and saves the original text as a
* backup.
*/
@Override
protected void onResume() {
super.onResume();
/*
* mCursor is initialized, since onCreate() always precedes onResume for any running
* process. This tests that it's not null, since it should always contain data.
*/
if (mCursor != null) {
// Requery in case something changed while paused (such as the title)
mCursor.requery();
/* Moves to the first record. Always call moveToFirst() before accessing data in
* a Cursor for the first time. The semantics of using a Cursor are that when it is
* created, its internal index is pointing to a "place" immediately before the first
* record.
*/
mCursor.moveToFirst();
// Modifies the window title for the Activity according to the current Activity state.
if (mState == STATE_EDIT) {
// Set the title of the Activity to include the note title
int colTitleIndex = mCursor.getColumnIndex(NotePad.Notes.COLUMN_NAME_TITLE);
String title = mCursor.getString(colTitleIndex);
Resources res = getResources();
String text = String.format(res.getString(R.string.title_edit), title);
setTitle(text);
// Sets the title to "create" for inserts
} else if (mState == STATE_INSERT) {
setTitle(getText(R.string.title_create));
}
/*
* onResume() may have been called after the Activity lost focus (was paused).
* The user was either editing or creating a note when the Activity paused.
* The Activity should re-display the text that had been retrieved previously, but
* it should not move the cursor. This helps the user to continue editing or entering.
*/
// Gets the note text from the Cursor and puts it in the TextView, but doesn't change
// the text cursor's position.
int colNoteIndex = mCursor.getColumnIndex(NotePad.Notes.COLUMN_NAME_NOTE);
String note = mCursor.getString(colNoteIndex);
mText.setTextKeepState(note);
// Stores the original note text, to allow the user to revert changes.
if (mOriginalContent == null) {
mOriginalContent = note;
}
/*
* Something is wrong. The Cursor should always contain data. Report an error in the
* note.
*/
} else {
setTitle(getText(R.string.error_title));
mText.setText(getText(R.string.error_message));
}
}
/**
* This method is called when an Activity loses focus during its normal operation, and is then
* later on killed. The Activity has a chance to save its state so that the system can restore
* it.
*
* Notice that this method isn't a normal part of the Activity lifecycle. It won't be called
* if the user simply navigates away from the Activity.
*/
@Override
protected void onSaveInstanceState(Bundle outState) {
// Save away the original text, so we still have it if the activity
// needs to be killed while paused.
outState.putString(ORIGINAL_CONTENT, mOriginalContent);
}
/**
* This method is called when the Activity loses focus.
*
* For Activity objects that edit information, onPause() may be the one place where changes are
* saved. The Android application model is predicated on the idea that "save" and "exit" aren't
* required actions. When users navigate away from an Activity, they shouldn't have to go back
* to it to complete their work. The act of going away should save everything and leave the
* Activity in a state where Android can destroy it if necessary.
*
* If the user hasn't done anything, then this deletes or clears out the note, otherwise it
* writes the user's work to the provider.
*/
@Override
protected void onPause() {
super.onPause();
/*
* Tests to see that the query operation didn't fail (see onCreate()). The Cursor object
* will exist, even if no records were returned, unless the query failed because of some
* exception or error.
*
*/
if (mCursor != null) {
// Get the current note text.
String text = mText.getText().toString();
int length = text.length();
/*
* If the Activity is in the midst of finishing and there is no text in the current
* note, returns a result of CANCELED to the caller, and deletes the note. This is done
* even if the note was being edited, the assumption being that the user wanted to
* "clear out" (delete) the note.
*/
if (isFinishing() && (length == 0)) {
setResult(RESULT_CANCELED);
deleteNote();
/*
* Writes the edits to the provider. The note has been edited if an existing note was
* retrieved into the editor *or* if a new note was inserted. In the latter case,
* onCreate() inserted a new empty note into the provider, and it is this new note
* that is being edited.
*/
} else if (mState == STATE_EDIT) {
// Creates a map to contain the new values for the columns
updateNote(text, null);
} else if (mState == STATE_INSERT) {
updateNote(text, text);
mState = STATE_EDIT;
}
}
}
/**
* This method is called when the user clicks the device's Menu button the first time for
* this Activity. Android passes in a Menu object that is populated with items.
*
* Builds the menus for editing and inserting, and adds in alternative actions that
* registered themselves to handle the MIME types for this application.
*
* @param menu A Menu object to which items should be added.
* @return True to display the menu.
*/
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate menu from XML resource
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.editor_options_menu, menu);
// Only add extra menu items for a saved note
if (mState == STATE_EDIT) {
// Append to the
// menu items for any other activities that can do stuff with it
// as well. This does a query on the system for any activities that
// implement the ALTERNATIVE_ACTION for our data, adding a menu item
// for each one that is found.
Intent intent = new Intent(null, mUri);
intent.addCategory(Intent.CATEGORY_ALTERNATIVE);
menu.addIntentOptions(Menu.CATEGORY_ALTERNATIVE, 0, 0,
new ComponentName(this, NoteEditor.class), null, intent, 0, null);
}
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// Check if note has changed and enable/disable the revert option
int colNoteIndex = mCursor.getColumnIndex(NotePad.Notes.COLUMN_NAME_NOTE);
String savedNote = mCursor.getString(colNoteIndex);
String currentNote = mText.getText().toString();
if (savedNote.equals(currentNote)) {
menu.findItem(R.id.menu_revert).setVisible(false);
} else {
menu.findItem(R.id.menu_revert).setVisible(true);
}
return super.onPrepareOptionsMenu(menu);
}
/**
* This method is called when a menu item is selected. Android passes in the selected item.
* The switch statement in this method calls the appropriate method to perform the action the
* user chose.
*
* @param item The selected MenuItem
* @return True to indicate that the item was processed, and no further work is necessary. False
* to proceed to further processing as indicated in the MenuItem object.
*/
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle all of the possible menu actions.
switch (item.getItemId()) {
case R.id.menu_save:
String text = mText.getText().toString();
updateNote(text, null);
finish();
break;
case R.id.menu_delete:
deleteNote();
finish();
break;
case R.id.menu_revert:
cancelNote();
break;
}
return super.onOptionsItemSelected(item);
}
/**
* A helper method that replaces the note's data with the contents of the clipboard.
*/
private final void performPaste() {
// Gets a handle to the Clipboard Manager
ClipboardManager clipboard = (ClipboardManager)
getSystemService(Context.CLIPBOARD_SERVICE);
// Gets a content resolver instance
ContentResolver cr = getContentResolver();
// Gets the clipboard data from the clipboard
ClipData clip = clipboard.getPrimaryClip();
if (clip != null) {
String text=null;
String title=null;
// Gets the first item from the clipboard data
ClipData.Item item = clip.getItemAt(0);
// Tries to get the item's contents as a URI pointing to a note
Uri uri = item.getUri();
// Tests to see that the item actually is an URI, and that the URI
// is a content URI pointing to a provider whose MIME type is the same
// as the MIME type supported by the Note pad provider.
if (uri != null && NotePad.Notes.CONTENT_ITEM_TYPE.equals(cr.getType(uri))) {
// The clipboard holds a reference to data with a note MIME type. This copies it.
Cursor orig = cr.query(
uri, // URI for the content provider
PROJECTION, // Get the columns referred to in the projection
null, // No selection variables
null, // No selection variables, so no criteria are needed
null // Use the default sort order
);
// If the Cursor is not null, and it contains at least one record
// (moveToFirst() returns true), then this gets the note data from it.
if (orig != null) {
if (orig.moveToFirst()) {
int colNoteIndex = mCursor.getColumnIndex(NotePad.Notes.COLUMN_NAME_NOTE);
int colTitleIndex = mCursor.getColumnIndex(NotePad.Notes.COLUMN_NAME_TITLE);
text = orig.getString(colNoteIndex);
title = orig.getString(colTitleIndex);
}
// Closes the cursor.
orig.close();
}
}
// If the contents of the clipboard wasn't a reference to a note, then
// this converts whatever it is to text.
if (text == null) {
text = item.coerceToText(this).toString();
}
// Updates the current note with the retrieved title and text.
updateNote(text, title);
}
}
/**
* Replaces the current note contents with the text and title provided as arguments.
* @param text The new note contents to use.
* @param title The new note title to use
*/
private final void updateNote(String text, String title) {
// Sets up a map to contain values to be updated in the provider.
ContentValues values = new ContentValues();
values.put(NotePad.Notes.COLUMN_NAME_MODIFICATION_DATE, System.currentTimeMillis());
// If the action is to insert a new note, this creates an initial title for it.
if (mState == STATE_INSERT) {
// If no title was provided as an argument, create one from the note text.
if (title == null) {
// Get the note's length
int length = text.length();
// Sets the title by getting a substring of the text that is 31 characters long
// or the number of characters in the note plus one, whichever is smaller.
title = text.substring(0, Math.min(30, length));
// If the resulting length is more than 30 characters, chops off any
// trailing spaces
if (length > 30) {
int lastSpace = title.lastIndexOf(' ');
if (lastSpace > 0) {
title = title.substring(0, lastSpace);
}
}
}
// In the values map, sets the value of the title
values.put(NotePad.Notes.COLUMN_NAME_TITLE, title);
} else if (title != null) {
// In the values map, sets the value of the title
values.put(NotePad.Notes.COLUMN_NAME_TITLE, title);
}
// This puts the desired notes text into the map.
values.put(NotePad.Notes.COLUMN_NAME_NOTE, text);
/*
* Updates the provider with the new values in the map. The ListView is updated
* automatically. The provider sets this up by setting the notification URI for
* query Cursor objects to the incoming URI. The content resolver is thus
* automatically notified when the Cursor for the URI changes, and the UI is
* updated.
* Note: This is being done on the UI thread. It will block the thread until the
* update completes. In a sample app, going against a simple provider based on a
* local database, the block will be momentary, but in a real app you should use
* android.content.AsyncQueryHandler or android.os.AsyncTask.
*/
getContentResolver().update(
mUri, // The URI for the record to update.
values, // The map of column names and new values to apply to them.
null, // No selection criteria are used, so no where columns are necessary.
null // No where columns are used, so no where arguments are necessary.
);
}
/**
* This helper method cancels the work done on a note. It deletes the note if it was
* newly created, or reverts to the original text of the note i
*/
private final void cancelNote() {
if (mCursor != null) {
if (mState == STATE_EDIT) {
// Put the original note text back into the database
mCursor.close();
mCursor = null;
ContentValues values = new ContentValues();
values.put(NotePad.Notes.COLUMN_NAME_NOTE, mOriginalContent);
getContentResolver().update(mUri, values, null, null);
} else if (mState == STATE_INSERT) {
// We inserted an empty note, make sure to delete it
deleteNote();
}
}
setResult(RESULT_CANCELED);
finish();
}
/**
* Take care of deleting a note. Simply deletes the entry.
*/
private final void deleteNote() {
if (mCursor != null) {
mCursor.close();
mCursor = null;
getContentResolver().delete(mUri, null, null);
mText.setText("");
}
}
}