Android 2.0 源码

/* * Copyright (C) 2006 The Android Open Source Project * * 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 android.view; import android.content.Context; import android.content.res.Resources; import android.content.res.TypedArray; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.LinearGradient; import android.graphics.Matrix; import android.graphics.Paint; import android.graphics.PixelFormat; import android.graphics.PorterDuff; import android.graphics.PorterDuffXfermode; import android.graphics.Rect; import android.graphics.Region; import android.graphics.Shader; import android.graphics.Point; import android.graphics.drawable.ColorDrawable; import android.graphics.drawable.Drawable; import android.os.Handler; import android.os.IBinder; import android.os.Message; import android.os.Parcel; import android.os.Parcelable; import android.os.RemoteException; import android.os.SystemClock; import android.os.SystemProperties; import android.util.AttributeSet; import android.util.EventLog; import android.util.Log; import android.util.SparseArray; import android.view.ContextMenu.ContextMenuInfo; import android.view.animation.Animation; import android.view.inputmethod.InputConnection; import android.view.inputmethod.InputMethodManager; import android.view.inputmethod.EditorInfo; import android.widget.ScrollBarDrawable; import com.android.internal.R; import com.android.internal.view.menu.MenuBuilder; import java.util.ArrayList; import java.util.Arrays; import java.lang.ref.SoftReference; /** * <p> * This class represents the basic building block for user interface components. A View * occupies a rectangular area on the screen and is responsible for drawing and * event handling. View is the base class for <em>widgets</em>, which are * used to create interactive UI components (buttons, text fields, etc.). The * {@link android.view.ViewGroup} subclass is the base class for <em>layouts</em>, which * are invisible containers that hold other Views (or other ViewGroups) and define * their layout properties. * </p> * * <div class="special"> * <p>For an introduction to using this class to develop your * application's user interface, read the Developer Guide documentation on * <strong><a href="{@docRoot}guide/topics/ui/index.html">User Interface</a></strong>. Special topics * include: * <br/><a href="{@docRoot}guide/topics/ui/declaring-layout.html">Declaring Layout</a> * <br/><a href="{@docRoot}guide/topics/ui/menus.html">Creating Menus</a> * <br/><a href="{@docRoot}guide/topics/ui/layout-objects.html">Common Layout Objects</a> * <br/><a href="{@docRoot}guide/topics/ui/binding.html">Binding to Data with AdapterView</a> * <br/><a href="{@docRoot}guide/topics/ui/ui-events.html">Handling UI Events</a> * <br/><a href="{@docRoot}guide/topics/ui/themes.html">Applying Styles and Themes</a> * <br/><a href="{@docRoot}guide/topics/ui/custom-components.html">Building Custom Components</a> * <br/><a href="{@docRoot}guide/topics/ui/how-android-draws.html">How Android Draws Views</a>. * </p> * </div> * * <a name="Using"></a> * <h3>Using Views</h3> * <p> * All of the views in a window are arranged in a single tree. You can add views * either from code or by specifying a tree of views in one or more XML layout * files. There are many specialized subclasses of views that act as controls or * are capable of displaying text, images, or other content. * </p> * <p> * Once you have created a tree of views, there are typically a few types of * common operations you may wish to perform: * <ul> * <li><strong>Set properties:</strong> for example setting the text of a * {@link android.widget.TextView}. The available properties and the methods * that set them will vary among the different subclasses of views. Note that * properties that are known at build time can be set in the XML layout * files.</li> * <li><strong>Set focus:</strong> The framework will handled moving focus in * response to user input. To force focus to a specific view, call * {@link #requestFocus}.</li> * <li><strong>Set up listeners:</strong> Views allow clients to set listeners * that will be notified when something interesting happens to the view. For * example, all views will let you set a listener to be notified when the view * gains or loses focus. You can register such a listener using * {@link #setOnFocusChangeListener}. Other view subclasses offer more * specialized listeners. For example, a Button exposes a listener to notify * clients when the button is clicked.</li> * <li><strong>Set visibility:</strong> You can hide or show views using * {@link #setVisibility}.</li> * </ul> * </p> * <p><em> * Note: The Android framework is responsible for measuring, laying out and * drawing views. You should not call methods that perform these actions on * views yourself unless you are actually implementing a * {@link android.view.ViewGroup}. * </em></p> * * <a name="Lifecycle"></a> * <h3>Implementing a Custom View</h3> * * <p> * To implement a custom view, you will usually begin by providing overrides for * some of the standard methods that the framework calls on all views. You do * not need to override all of these methods. In fact, you can start by just * overriding {@link #onDraw(android.graphics.Canvas)}. * <table border="2" width="85%" align="center" cellpadding="5"> * <thead> * <tr><th>Category</th> <th>Methods</th> <th>Description</th></tr> * </thead> * * <tbody> * <tr> * <td rowspan="2">Creation</td> * <td>Constructors</td> * <td>There is a form of the constructor that are called when the view * is created from code and a form that is called when the view is * inflated from a layout file. The second form should parse and apply * any attributes defined in the layout file. * </td> * </tr> * <tr> * <td><code>{@link #onFinishInflate()}</code></td> * <td>Called after a view and all of its children has been inflated * from XML.</td> * </tr> * * <tr> * <td rowspan="3">Layout</td> * <td><code>{@link #onMeasure}</code></td> * <td>Called to determine the size requirements for this view and all * of its children. * </td> * </tr> * <tr> * <td><code>{@link #onLayout}</code></td> * <td>Called when this view should assign a size and position to all * of its children. * </td> * </tr> * <tr> * <td><code>{@link #onSizeChanged}</code></td> * <td>Called when the size of this view has changed. * </td> * </tr> * * <tr> * <td>Drawing</td> * <td><code>{@link #onDraw}</code></td> * <td>Called when the view should render its content. * </td> * </tr> * * <tr> * <td rowspan="4">Event processing</td> * <td><code>{@link #onKeyDown}</code></td> * <td>Called when a new key event occurs. * </td> * </tr> * <tr> * <td><code>{@link #onKeyUp}</code></td> * <td>Called when a key up event occurs. * </td> * </tr> * <tr> * <td><code>{@link #onTrackballEvent}</code></td> * <td>Called when a trackball motion event occurs. * </td> * </tr> * <tr> * <td><code>{@link #onTouchEvent}</code></td>