Android Drawable完全解析（一）：Drawable源码分析（上）
Android Drawable完全解析（一）：Drawable源码分析（中）
Android Drawable完全解析（一）：Drawable源码分析（下）
呃…我不是故意要凑篇幅写个什么上下篇，实在是因为Drawable源码有点长，一篇写不下啦O(∩_∩)O~
上一篇文章 其实你不懂：Drawable着色(tint)的兼容方案 源码解析 描述了Drawable的着色原理，文章里有涉及到Drawable的一些方法，顺便看一下Drawabld的源码，发现Drawable涉及的面很广，尤其是竟然有那么多的继承类。想想自己平时也就用过ColorDrawable,StateListDrawable,BitmapDrawable很有限的几个子类，对于Drawable的应用还是太零散了，所以写这个Drawable系列文章，对其做一个相对完整的分析！
这是“Drawable完全解析”系列文章的第一篇，就从Drawable的源码分析开始！
1:Drawable与其子类的继承关系
直接看图，暂不详细介绍具体使用方法。
Drawable及其子类继承关系.png
可以看到Drawable竟然有这么多子类，真的需要花一些时间才能分别搞得清楚。
2:Drawable源码分析/翻译
此处源码是SDK 24版本下的Drawable.java文件，不同版本下应该会有出入，敬请注意！
源码较长，英文较好的同学记得指出我翻译和理解的错误！
package android.graphics.drawable;
import com.android.internal.R;
*****略
/** Drawable是一个用于处理各种可绘制资源的抽象类。我们使用Drawable最常见的情况就是将获取到的资源绘制到屏幕上；Drawable类提供了一些通用的API来处理以下具有多种表现形式的可视资源/视觉资源。 * A Drawable is a general abstraction for "something that can be drawn." Most * often you will deal with Drawable as the type of resource retrieved for * drawing things to the screen; the Drawable class provides a generic API for * dealing with an underlying visual resource that may take a variety of forms. 和View不同，Drawable实例不具备任何能力接收事件或与用户交互。 * Unlike a {@link android.view.View}, a Drawable does not have any facility to * receive events or otherwise interact with the user. * 除了简单绘图，Drawable提供了一些通用的机制使客户端与当前正在绘制的内容进行交互。 * <p>In addition to simple drawing, Drawable provides a number of generic * mechanisms for its client to interact with what is being drawn: * setBounds方法必须被Drawable实例调用，用于声明Drawable实例绘制的位置和大小。所有的Drawable实例都会生成请求的尺寸，这一点通常可以通过缩放图像很容易就达到。对一些Drawable实例，客户端可以通过调用getIntrinsicHeight和getIntrinsicWidth方法得到其首选尺寸。 * <ul> * <li> The {@link #setBounds} method <var>must</var> be called to tell the * Drawable where it is drawn and how large it should be. All Drawables * should respect the requested size, often simply by scaling their * imagery. A client can find the preferred size for some Drawables with * the {@link #getIntrinsicHeight} and {@link #getIntrinsicWidth} methods. getPadding会将Drawable实例与实例中内容的间隔信息存储在Rect实例中。 * <li> The {@link #getPadding} method can return from some Drawables * information about how to frame content that is placed inside of them. 例如，一个Drawable实例作为一个Button的背景，Button控件实例需要返回padding值用来放置Button控件显示的内容。 * For example, a Drawable that is intended to be the frame for a button * widget would need to return padding that correctly places the label * inside of itself. * setState方法允许客户端告知Drawable实例在什么状态下才进行绘制。 例如“焦点获取状态”，“选中状态”等等。某些Drawable可能会根据选定的状态值变更它们的外观。 * <li> The {@link #setState} method allows the client to tell the Drawable * in which state it is to be drawn, such as "focused", "selected", etc. * Some drawables may modify their imagery based on the selected state. * setLevel方法允许客户端提供一个单一的连续控制器来编辑正在显示的Drawable实例，例如电量水平或者进度值。某些Drawable实例可以根据当前的level值变更它们的外观。 * <li> The {@link #setLevel} method allows the client to supply a single * continuous controller that can modify the Drawable is displayed, such as * a battery level or progress level. Some drawables may modify their * imagery based on the current level. * 通过Callback接口，一个Drawable实例可以回调其客户端来执行动画。为了动画可以被执行，所有的客户端都应该支持这个Callback接口。实现这一效果最简单的方法就是通过系统提供的机制，例如ImageView，View.setBackgoound方法。 * <li> A Drawable can perform animations by calling back to its client * through the {@link Callback} interface. All clients should support this * interface (via {@link #setCallback}) so that animations will work. A * simple way to do this is through the system facilities such as * {@link android.view.View#setBackground(Drawable)} and * {@link android.widget.ImageView}. * </ul> * 尽管通常情况下对应用不可见，Drawable实例可能存在以下多种形式： Bitmap:最简单的Drawable形式，PNG或者JPEG图片。 .9图：PNG的一个扩展，可以支持设置其如何填充内容，如何被拉伸。 Shape：包含简单的绘制指令，用于替代bitmap，某些情况下对大小调整有更好表现。 Layers：一个复合的Drawable，按照层级进行绘制，单个Drawable实例绘制于其下层Drawable实例集合之上。 States：一个复合的Drawable，根据它的state选择一个Drawable集合。 Levels：一个复合的Drawable，根据它的level选择一个Drawable集合。 Scale：一个复合的Drawable和单个Drawable实例构成，它的总体尺寸由它的当前level值决定。 * Though usually not visible to the application, Drawables may take a variety * of forms: * * <ul> * <li> <b>Bitmap</b>: the simplest Drawable, a PNG or JPEG image. * <li> <b>Nine Patch</b>: an extension to the PNG format allows it to * specify information about how to stretch it and place things inside of * it. * <li> <b>Shape</b>: contains simple drawing commands instead of a raw * bitmap, allowing it to resize better in some cases. * <li> <b>Layers</b>: a compound drawable, which draws multiple underlying * drawables on top of each other. * <li> <b>States</b>: a compound drawable that selects one of a set of * drawables based on its state. * <li> <b>Levels</b>: a compound drawable that selects one of a set of * drawables based on its level. * <li> <b>Scale</b>: a compound drawable with a single child drawable, * whose overall size is modified based on the current level. * </ul> * 自定义Drawable 所有的Android版本都支持框架层提供的Drawable类被扩展/自定义和应用于运行时。从Android版本24开始，自定义Drawable可以在XML中直接使用。 * <a name="Custom"></a> * <h3>Custom drawables</h3> * * <p> * All versions of Android allow the Drawable class to be extended and used at * run time in place of framework-provided drawable classes. Starting in * {@link android.os.Build.VERSION_CODES#N API 24}, custom drawables classes * may also be used in XML. * <p> 注： 自定义Drawable仅能应用于当前应用，其他应用无法加载它们。 自定义Drawable必须继承Drawable类，至少重写draw方法以绘制内容。 * <strong>Note:</strong> Custom drawable classes are only accessible from * within your application package. Other applications will not be able to load * them. * <p> * At a minimum, custom drawable classes must implement the abstract methods on * Drawable and should override the {@link Drawable#draw(Canvas)} method to * draw content. 自定义Drawable用于XML中有多种方式： 1：直接引用自定义Drawable类名的全称，且该类必须为公共顶层类。 2：使用drawable作为XML的元素名称，指定该自定义Drawable类的全称。该自定义Drawable类可以是 公共顶层类或者公共静态内部类。 * <p> * Custom drawables classes may be used in XML in multiple ways: * <ul> * <li> * Using the fully-qualified class name as the XML element name. For * this method, the custom drawable class must be a public top-level * class. * <pre> * <com.myapp.MyCustomDrawable xmlns:android="http://schemas.android.com/apk/res/android" * android:color="#ffff0000" /> * </pre> * </li> * <li> * Using <em>drawable</em> as the XML element name and specifying the * fully-qualified class name from the <em>class</em> attribute. This * method may be used for both public top-level classes and public * static inner classes. * <pre> * <drawable xmlns:android="http://schemas.android.com/apk/res/android" * class="com.myapp.MyTopLevelClass$InnerCustomDrawable" * android:color="#ffff0000" /> * </pre> * </li> * </ul> * 略 */
public abstract class Drawable {
private static final Rect ZERO_BOUNDS_RECT = new Rect();
static final PorterDuff.Mode DEFAULT_TINT_MODE = PorterDuff.Mode.SRC_IN;
private int[] mStateSet = StateSet.WILD_CARD;
private int mLevel = 0;
private @Config int mChangingConfigurations = 0;
private Rect mBounds = ZERO_BOUNDS_RECT; // lazily becomes a new Rect()
private WeakReference<Callback> mCallback = null;
private boolean mVisible = true;
private int mLayoutDirection;
/** 在通过setBounds设置的范围内进行绘制，通过调用setAlpha和setColorFilter 等方法可以影响绘制的效果。 canvas：当前Drawable实例要被绘制到canvas上。 * Draw in its bounds (set via setBounds) respecting optional effects such * as alpha (set via setAlpha) and color filter (set via setColorFilter). * * @param canvas The canvas to draw into */
public abstract void draw(@NonNull Canvas canvas);
/** 为当前Drawable实例设置一个矩形范围，在draw方法调用时候， Drawable实例将被绘制到这个矩形范围内。 * Specify a bounding rectangle for the Drawable. This is where the drawable * will draw when its draw() method is called. */
public void setBounds(int left, int top, int right, int bottom) {
Rect oldBounds = mBounds;
if (oldBounds == ZERO_BOUNDS_RECT) {
oldBounds = mBounds = new Rect();
}
if (oldBounds.left != left || oldBounds.top != top ||
oldBounds.right != right || oldBounds.bottom != bottom) {
if (!oldBounds.isEmpty()) {
// first invalidate the previous bounds
invalidateSelf();
}
mBounds.set(left, top, right, bottom);
onBoundsChange(mBounds);
}
}
public void setBounds(@NonNull Rect bounds) {
setBounds(bounds.left, bounds.top, bounds.right, bounds.bottom);
}
/** 将当前Drawable实例通过setBounds设置的绘制范围拷贝到客户端提供的Rect实例中返回 * Return a copy of the drawable's bounds in the specified Rect (allocated * by the caller). The bounds specify where this will draw when its draw() * method is called. * * @param bounds Rect to receive the drawable's bounds (allocated by the * caller). */
public final void copyBounds(@NonNull Rect bounds) {
bounds.set(mBounds);
}
public final Rect copyBounds() {
return new Rect(mBounds);
}
/** 返回当前Drawable实例的矩形绘制范围。注：返回的矩形就是 当前Drawable实际的绘制范围矩形，所以如果是需要一个拷贝的矩形范围， 应该调用copyBounds来代替。 调用getBounds，你不能修改返回的矩形，会影响Drawable实例。 * Return the drawable's bounds Rect. Note: for efficiency, the returned * object may be the same object stored in the drawable (though this is not * guaranteed), so if a persistent copy of the bounds is needed, call * copyBounds(rect) instead. * You should also not change the object returned by this method as it may * be the same object stored in the drawable. * * @return The bounds of the drawable (which may change later, so caller * beware). DO NOT ALTER the returned object as it may change the * stored bounds of this drawable. * * @see #copyBounds() * @see #copyBounds(android.graphics.Rect) */
@NonNull
public final Rect getBounds() {
if (mBounds == ZERO_BOUNDS_RECT) {
mBounds = new Rect();
}
return mBounds;
}
/** 返回当前Drawable实例的模糊绘制范围矩形。 注：返回的矩形和当前Drawable绘制返回矩形是同一个对象。 * Return the drawable's dirty bounds Rect. Note: for efficiency, the * returned object may be the same object stored in the drawable (though * this is not guaranteed). * <p> * By default, this returns the full drawable bounds. Custom drawables may * override this method to perform more precise invalidation. * * @return The dirty bounds of this drawable */
@NonNull
public Rect getDirtyBounds() {
return getBounds();
}
/** 这段我没怎么看懂，勉强翻译一下，哪位同学懂可以留言！ 为配置参数设置一个标记，当该配置参数变更时可能改变当前 Drawable实例，要求当前Drawable实例重新创建。 * Set a mask of the configuration parameters for which this drawable * may change, requiring that it be re-created. * * @param configs A mask of the changing configuration parameters, as * defined by {@link android.content.pm.ActivityInfo}. * * @see android.content.pm.ActivityInfo */
public void setChangingConfigurations(@Config int configs) {
mChangingConfigurations = configs;
}
public @Config int getChangingConfigurations() {
return mChangingConfigurations;
}
/** 当设置为true，该Drawable实例在绘制到一个低于8-bits每单位色值 的设备上时候颜色将发生‘抖动’？ * Set to true to have the drawable dither its colors when drawn to a * device with fewer than 8-bits per color component. * * @see android.graphics.Paint#setDither(boolean); * @deprecated This property is ignored. */
@Deprecated
public void setDither(boolean dither) {}
/** 当设置为true,则该Drawable实例在缩放或者旋转时候将 对它关联的bitmap进行滤波过滤。可以提升旋转时的绘制效果。 如果该Drawable实例未使用bitmap,这个方法无作用。 * Set to true to have the drawable filter its bitmaps with bilinear * sampling when they are scaled or rotated. * * <p>This can improve appearance when bitmaps are rotated. If the drawable * does not use bitmaps, this call is ignored.</p> * * @see #isFilterBitmap() * @see android.graphics.Paint#setFilterBitmap(boolean); */
public void setFilterBitmap(boolean filter) {}
public boolean isFilterBitmap() {
return false;
}
/** 一个回调接口，用于调度和执行Drawable实例的动画。 如果要实现自定义的动画Drawable,就需要实现这个接口。 * Implement this interface if you want to create an animated drawable that * extends {@link android.graphics.drawable.Drawable Drawable}. * Upon retrieving a drawable, use * {@link Drawable#setCallback(android.graphics.drawable.Drawable.Callback)} * to supply your implementation of the interface to the drawable; it uses * this interface to schedule and execute animation changes. */
public interface Callback {
/** Drawable实例被重绘时候调用。在当前Drawable实例位置的View 实例需要重绘，或者至少部分重绘。 * Called when the drawable needs to be redrawn. A view at this point * should invalidate itself (or at least the part of itself where the * drawable appears). * * @param who The drawable that is requesting the update. */
void invalidateDrawable(@NonNull Drawable who);
/** 一个Drawable实例可以调用这个方法预先安排动画的下一帧。 也可以通过Handler.postAtTime实现。 * A Drawable can call this to schedule the next frame of its * animation. An implementation can generally simply call * {@link android.os.Handler#postAtTime(Runnable, Object, long)} with * the parameters <var>(what, who, when)</var> to perform the * scheduling. * * @param who The drawable being scheduled. * @param what The action to execute. * @param when The time (in milliseconds) to run. The timebase is * {@link android.os.SystemClock#uptimeMillis} */
void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when);
/** 一个Drawable实例可以调用这个方法取消之前安排的某一帧。 也可以通过Handler.removeCallbacks实现。 * A Drawable can call this to unschedule an action previously * scheduled with {@link #scheduleDrawable}. An implementation can * generally simply call * {@link android.os.Handler#removeCallbacks(Runnable, Object)} with * the parameters <var>(what, who)</var> to unschedule the drawable. * * @param who The drawable being unscheduled. * @param what The action being unscheduled. */
void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what);
}
/** 如果客户端要求支持动画Drawable,将一个Callback实例绑定到当前 Drawable实例上。 * Bind a {@link Callback} object to this Drawable. Required for clients * that want to support animated drawables. * * @param cb The client's Callback implementation. * * @see #getCallback() */
public final void setCallback(@Nullable Callback cb) {
mCallback = cb != null ? new WeakReference<>(cb) : null;
}
public Callback getCallback() {
return mCallback != null ? mCallback.get() : null;
}
/** 通过由调用setCallBack设置过的Callback实例执行 invalidateDrawable。如果没有调用过setCallback，则无效果 * Use the current {@link Callback} implementation to have this Drawable * redrawn. Does nothing if there is no Callback attached to the * Drawable. * * @see Callback#invalidateDrawable * @see #getCallback() * @see #setCallback(android.graphics.drawable.Drawable.Callback) */
public void invalidateSelf() {
final Callback callback = getCallback();
if (callback != null) {
callback.invalidateDrawable(this);
}
}
/** 通过由调用setCallBack设置过的Callback实例执行 scheduleDrawable。如果没有调用过setCallback，则无效果 * Use the current {@link Callback} implementation to have this Drawable * scheduled. Does nothing if there is no Callback attached to the * Drawable. * * @param what The action being scheduled. * @param when The time (in milliseconds) to run. * * @see Callback#scheduleDrawable */
public void scheduleSelf(@NonNull Runnable what, long when) {
final Callback callback = getCallback();
if (callback != null) {
callback.scheduleDrawable(this, what, when);
}
}
/** 通过由调用setCallBack设置过的Callback实例执行 unscheduleDrawable。如果没有调用过setCallback，则无效果 * Use the current {@link Callback} implementation to have this Drawable * unscheduled. Does nothing if there is no Callback attached to the * Drawable. * * @param what The runnable that you no longer want called. * * @see Callback#unscheduleDrawable */
public void unscheduleSelf(@NonNull Runnable what) {
final Callback callback = getCallback();
if (callback != null) {
callback.unscheduleDrawable(this, what);
}
}
/** 获取当前Drawable实例的布局方向。 * Returns the resolved layout direction for this Drawable. * * @return One of {@link android.view.View#LAYOUT_DIRECTION_LTR}, * {@link android.view.View#LAYOUT_DIRECTION_RTL} * @see #setLayoutDirection(int) */
public @View.ResolvedLayoutDir int getLayoutDirection() {
return mLayoutDirection;
}
/** 设置当前Drawable实例的布局方向。 * Set the layout direction for this drawable. Should be a resolved * layout direction, as the Drawable has no capacity to do the resolution on * its own. * * @param layoutDirection the resolved layout direction for the drawable, * either {@link android.view.View#LAYOUT_DIRECTION_LTR} * or {@link android.view.View#LAYOUT_DIRECTION_RTL} * @return {@code true} if the layout direction change has caused the * appearance of the drawable to change such that it needs to be * re-drawn, {@code false} otherwise * @see #getLayoutDirection() */
public final boolean setLayoutDirection(@View.ResolvedLayoutDir int layoutDirection) {
if (mLayoutDirection != layoutDirection) {
//如果当前Drawable布局方向和layoutDirection不一致，
//则修改布局方向为layoutDirection，然后执行onLayoutDirectionChanged
mLayoutDirection = layoutDirection;
return onLayoutDirectionChanged(layoutDirection);
}
return false;
}
/** 当调用setLayoutDirection方法，Drawable布局方向发生变化后调用 * Called when the drawable's resolved layout direction changes. * * @param layoutDirection the new resolved layout direction * @return {@code true} if the layout direction change has caused the * appearance of the drawable to change such that it needs to be * re-drawn, {@code false} otherwise * @see #setLayoutDirection(int) */
public boolean onLayoutDirectionChanged(@View.ResolvedLayoutDir int layoutDirection) {
return false;
}
/** 设置Drawable实例的透明度。 0：完全透明 255:完全不透明 * Specify an alpha value for the drawable. 0 means fully transparent, and * 255 means fully opaque. */
public abstract void setAlpha(@IntRange(from=0,to=255) int alpha);
@IntRange(from=0,to=255)
public int getAlpha() {
return 0xFF;
}
/** 被隐匿 * @hide * * Internal-only method for setting xfermode on certain supported drawables. * * Should not be made public since the layers and drawing area with which * Drawables draw is private implementation detail, and not something apps * should rely upon. */
public void setXfermode(@Nullable Xfermode mode) {
// Base implementation drops it on the floor for compatibility. Whee!
}
/** 为当前Drawable实例设置颜色滤镜 * Specify an optional color filter for the drawable. * <p> * If a Drawable has a ColorFilter, each output pixel of the Drawable's * drawing contents will be modified by the color filter before it is * blended onto the render target of a Canvas. * </p> * <p> * Pass {@code null} to remove any existing color filter. * </p> * <p class="note"><strong>Note:</strong> Setting a non-{@code null} color * filter disables {@link #setTintList(ColorStateList) tint}. * </p> * * @param colorFilter The color filter to apply, or {@code null} to remove the * existing color filter */
public abstract void setColorFilter(@Nullable ColorFilter colorFilter);
/** 为当前Drawable实例设置滤镜效果 * Specify a color and Porter-Duff mode to be the color filter for this * drawable. * <p> * Convenience for {@link #setColorFilter(ColorFilter)} which constructs a * {@link PorterDuffColorFilter}. * </p> * <p class="note"><strong>Note:</strong> Setting a color filter disables * {@link #setTintList(ColorStateList) tint}. * </p> */
public void setColorFilter(@ColorInt int color, @NonNull PorterDuff.Mode mode) {
setColorFilter(new PorterDuffColorFilter(color, mode));
}
/** 为当前Drawable实例着色 * Specifies tint color for this drawable. * <p> 当前Drawable实例的绘制内容在被绘制到屏幕上之前将被指定颜色着色 当前方法和setColorFilter类似。 * A Drawable's drawing content will be blended together with its tint * before it is drawn to the screen. This functions similarly to * {@link #setColorFilter(int, PorterDuff.Mode)}. * </p> * <p> * To clear the tint, pass {@code null} to * {@link #setTintList(ColorStateList)}. * </p> * <p class="note"><strong>Note:</strong> Setting a color filter via * {@link #setColorFilter(ColorFilter)} or * {@link #setColorFilter(int, PorterDuff.Mode)} overrides tint. * </p> * * @param tintColor Color to use for tinting this drawable * @see #setTintList(ColorStateList) * @see #setTintMode(PorterDuff.Mode) */
public void setTint(@ColorInt int tintColor) {
setTintList(ColorStateList.valueOf(tintColor));
}
/** 根据ColorStateList对当前Drawable实例进行着色 这个一个空方法！！！在上一篇文章中已经指出，Drawabld的子类 实现了这个方法。 * Specifies tint color for this drawable as a color state list. * <p> * A Drawable's drawing content will be blended together with its tint * before it is drawn to the screen. This functions similarly to * {@link #setColorFilter(int, PorterDuff.Mode)}. * </p> * <p class="note"><strong>Note:</strong> Setting a color filter via * {@link #setColorFilter(ColorFilter)} or * {@link #setColorFilter(int, PorterDuff.Mode)} overrides tint. * </p> * * @param tint Color state list to use for tinting this drawable, or * {@code null} to clear the tint * @see #setTint(int) * @see #setTintMode(PorterDuff.Mode) */
public void setTintList(@Nullable ColorStateList tint) {}
/** 设置当前Drawable实例着色的过滤模式 * Specifies a tint blending mode for this drawable. * <p> * Defines how this drawable's tint color should be blended into the drawable * before it is drawn to screen. Default tint mode is {@link PorterDuff.Mode#SRC_IN}. * </p> * <p class="note"><strong>Note:</strong> Setting a color filter via * {@link #setColorFilter(ColorFilter)} or * {@link #setColorFilter(int, PorterDuff.Mode)} overrides tint. * </p> * * @param tintMode A Porter-Duff blending mode * @see #setTint(int) * @see #setTintList(ColorStateList) */
public void setTintMode(@NonNull PorterDuff.Mode tintMode) {}
public @Nullable ColorFilter getColorFilter() {
return null;
}
/** 取消当前Drawable实例的滤镜。 * Removes the color filter for this drawable. */
public void clearColorFilter() {
setColorFilter(null);
}
/** 设置当前Drawable实例热点区域的中心点坐标 * Specifies the hotspot's location within the drawable. * * @param x The X coordinate of the center of the hotspot * @param y The Y coordinate of the center of the hotspot */
public void setHotspot(float x, float y) {}
/** 设置当前Drawable实例的热点区域的边界 * Sets the bounds to which the hotspot is constrained, if they should be * different from the drawable bounds. * * @param left position in pixels of the left bound * @param top position in pixels of the top bound * @param right position in pixels of the right bound * @param bottom position in pixels of the bottom bound * @see #getHotspotBounds(android.graphics.Rect) */
public void setHotspotBounds(int left, int top, int right, int bottom) {}
/** * Populates {@code outRect} with the hotspot bounds. * * @param outRect the rect to populate with the hotspot bounds * @see #setHotspotBounds(int, int, int, int) */
public void getHotspotBounds(@NonNull Rect outRect) {
outRect.set(getBounds());
}
/** 被隐匿 * Whether this drawable requests projection. * * @hide magic! */
public boolean isProjected() {
return false;
}
/** 标示当前Drawable实例的外观是否要根据state进行变更。 客户端可以用这个方法判断是否有必要计算state并调用setState。 * Indicates whether this drawable will change its appearance based on * state. Clients can use this to determine whether it is necessary to * calculate their state and call setState. * * @return True if this drawable changes its appearance based on state, * false otherwise. * @see #setState(int[]) */
public boolean isStateful() {
return false;
}
/** 为当前Drawable实例设置一个状态值集合。当现有状态和stateSet 不同时候，触发onStateChange(stateSet)方法。 * Specify a set of states for the drawable. These are use-case specific, * so see the relevant documentation. As an example, the background for * widgets like Button understand the following states: * [{@link android.R.attr#state_focused}, * {@link android.R.attr#state_pressed}]. * * <p>If the new state you are supplying causes the appearance of the * Drawable to change, then it is responsible for calling * {@link #invalidateSelf} in order to have itself redrawn, <em>and</em> * true will be returned from this function. * * <p>Note: The Drawable holds a reference on to <var>stateSet</var> * until a new state array is given to it, so you must not modify this * array during that time.</p> * * @param stateSet The new set of states to be displayed. * * @return Returns true if this change in state has caused the appearance * of the Drawable to change (hence requiring an invalidate), otherwise * returns false. */
public boolean setState(@NonNull final int[] stateSet) {
if (!Arrays.equals(mStateSet, stateSet)) {
mStateSet = stateSet;
return onStateChange(stateSet);
}
return false;
}
/** * Describes the current state, as a union of primitve states, such as * {@link android.R.attr#state_focused}, * {@link android.R.attr#state_selected}, etc. * Some drawables may modify their imagery based on the selected state. * @return An array of resource Ids describing the current state. */
public @NonNull int[] getState() {
return mStateSet;
}
/** 如果当前Drawable实例在执行过渡动画，要求当前实例 立即跳转到当前状态并跳过任何正在执行的动画。 * If this Drawable does transition animations between states, ask that * it immediately jump to the current state and skip any active animations. */
public void jumpToCurrentState() {
}
/** 返回当前Drawable实例正在使用的Drawable实例， 对于一般单个Drawable，返回值就是自身，对于像StateListDrawable 这样的复合Drawable实例，则返回其持有的一个子Drawable实例。 * @return The current drawable that will be used by this drawable. For simple drawables, this * is just the drawable itself. For drawables that change state like * {@link StateListDrawable} and {@link LevelListDrawable} this will be the child drawable * currently in use. */
public @NonNull Drawable getCurrent() {
return this;
}
/** 为当前Drawable实例设置图像级别，从0到10000。setLevel使得 Drawable实例可以通过一个不断变化的控制器来变更它的图像， 例如音量等级或者进度。 * Specify the level for the drawable. This allows a drawable to vary its * imagery based on a continuous controller, for example to show progress * or volume level. * * <p>If the new level you are supplying causes the appearance of the * Drawable to change, then it is responsible for calling * {@link #invalidateSelf} in order to have itself redrawn, <em>and</em> * true will be returned from this function. * * @param level The new level, from 0 (minimum) to 10000 (maximum). * * @return Returns true if this change in level has caused the appearance * of the Drawable to change (hence requiring an invalidate), otherwise * returns false. */
public final boolean setLevel(@IntRange(from=0,to=10000) int level) {
if (mLevel != level) {
//修改图像等级为level，并调用onLevelChange
mLevel = level;
return onLevelChange(level);
}
return false;
}
/** * Retrieve the current level. * * @return int Current level, from 0 (minimum) to 10000 (maximum). */
public final @IntRange(from=0,to=10000) int getLevel() {
return mLevel;
}
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当前文章长度正在接近简书的限度，请考虑分篇书写吧
~~~~(>_<)~~~~
/** 设置当前Drawable实例是否可见，并不会影响Drawable实例的行为， 但是可以被某些Drawable来控制是否执行动画。 例如：AnimationDrawable可以通过这个方法启动或者停止动画， 后续文章会有验证。 * Set whether this Drawable is visible. This generally does not impact * the Drawable's behavior, but is a hint that can be used by some * Drawables, for example, to decide whether run animations. * * @param visible Set to true if visible, false if not. * @param restart You can supply true here to force the drawable to behave * as if it has just become visible, even if it had last * been set visible. Used for example to force animations * to restart. * * @return boolean Returns true if the new visibility is different than * its previous state. */
public boolean setVisible(boolean visible, boolean restart) {
boolean changed = mVisible != visible;
if (changed) {
mVisible = visible;
invalidateSelf();
}
return changed;
}
public final boolean isVisible() {
return mVisible;
}
/** 设置当前Drawable实例是不是自动被“镜像”/左右对调 当它的布局模式是从右到左 * Set whether this Drawable is automatically mirrored when its layout direction is RTL * (right-to left). See {@link android.util.LayoutDirection}. * * @param mirrored Set to true if the Drawable should be mirrored, false if not. */
public void setAutoMirrored(boolean mirrored) {
}
/** * Tells if this Drawable will be automatically mirrored when its layout direction is RTL * right-to-left. See {@link android.util.LayoutDirection}. * * @return boolean Returns true if this Drawable will be automatically mirrored. */
public boolean isAutoMirrored() {
return false;
}
/** 为当前Drawable实例和它的子实例应用指定的主题 * Applies the specified theme to this Drawable and its children. * * @param t the theme to apply */
public void applyTheme(@NonNull @SuppressWarnings("unused") Theme t) {
//空方法，Drawable子类会做自定义实现
}
public boolean canApplyTheme() {
return false;
}
/** 返回当前Drawable实例的透明或者不透明。返回值是其中之一： {@link android.graphics.PixelFormat#UNKNOWN}-透明度未知 {@link android.graphics.PixelFormat#TRANSLUCENT}-半透明 {@link android.graphics.PixelFormat#TRANSPARENT}-完全透明 {@link android.graphics.PixelFormat#OPAQUE}-完全不透明 如果Drawable中的内容可见性不确定，最安全的方案 是返回TRANSLUCENT/半透明 * Return the opacity/transparency of this Drawable. The returned value is * one of the abstract format constants in * {@link android.graphics.PixelFormat}: * {@link android.graphics.PixelFormat#UNKNOWN}, * {@link android.graphics.PixelFormat#TRANSLUCENT}, * {@link android.graphics.PixelFormat#TRANSPARENT}, or * {@link android.graphics.PixelFormat#OPAQUE}. * * <p>An OPAQUE drawable is one that draws all all content within its bounds, completely * covering anything behind the drawable. A TRANSPARENT drawable is one that draws nothing * within its bounds, allowing everything behind it to show through. A TRANSLUCENT drawable * is a drawable in any other state, where the drawable will draw some, but not all, * of the content within its bounds and at least some content behind the drawable will * be visible. If the visibility of the drawable's contents cannot be determined, the * safest/best return value is TRANSLUCENT. * * <p>Generally a Drawable should be as conservative as possible with the * value it returns. For example, if it contains multiple child drawables * and only shows one of them at a time, if only one of the children is * TRANSLUCENT and the others are OPAQUE then TRANSLUCENT should be * returned. You can use the method {@link #resolveOpacity} to perform a * standard reduction of two opacities to the appropriate single output. * * <p>Note that the returned value does not necessarily take into account a * custom alpha or color filter that has been applied by the client through * the {@link #setAlpha} or {@link #setColorFilter} methods. Some subclasses, * such as {@link BitmapDrawable}, {@link ColorDrawable}, and {@link GradientDrawable}, * do account for the value of {@link #setAlpha}, but the general behavior is dependent * upon the implementation of the subclass. * * @return int The opacity class of the Drawable. * * @see android.graphics.PixelFormat */
public abstract @PixelFormat.Opacity int getOpacity();
/** 根据两个不透明度值，返回合适的值。 两个不透明度值若相等，直接返回； 否则如果两个透明度值有至少一个是UNKNOWN，返回UNKNOWN； 否则如果两个透明度值有至少一个是TRANSLUCENT，返回TRANSLUCENT； 否则如果两个透明度值有至少一个是TRANSPARENT，返回TRANSPARENT； 否则返回OPAQUE； * Return the appropriate opacity value for two source opacities. If * either is UNKNOWN, that is returned; else, if either is TRANSLUCENT, * that is returned; else, if either is TRANSPARENT, that is returned; * else, OPAQUE is returned. * * <p>This is to help in implementing {@link #getOpacity}. * * @param op1 One opacity value. * @param op2 Another opacity value. * * @return int The combined opacity value. * * @see #getOpacity */
public static @PixelFormat.Opacity int resolveOpacity(@PixelFormat.Opacity int op1, @PixelFormat.Opacity int op2) {
if (op1 == op2) {
return op1;
}
if (op1 == PixelFormat.UNKNOWN || op2 == PixelFormat.UNKNOWN) {
return PixelFormat.UNKNOWN;
}
if (op1 == PixelFormat.TRANSLUCENT || op2 == PixelFormat.TRANSLUCENT) {
return PixelFormat.TRANSLUCENT;
}
if (op1 == PixelFormat.TRANSPARENT || op2 == PixelFormat.TRANSPARENT) {
return PixelFormat.TRANSPARENT;
}
return PixelFormat.OPAQUE;
}
/** 返回在当前Drawable实例中完全透明的一个区域。 这个区域可以用来影响绘制操作，定义当前Drawable实例的目标 在渲染当前Drawable实例时候哪个区域不需要改变。 * Returns a Region representing the part of the Drawable that is completely * transparent. This can be used to perform drawing operations, identifying * which parts of the target will not change when rendering the Drawable. * The default implementation returns null, indicating no transparent * region; subclasses can optionally override this to return an actual * Region if they want to supply this optimization information, but it is * not required that they do so. * * @return Returns null if the Drawables has no transparent region to * report, else a Region holding the parts of the Drawable's bounds that * are transparent. */
public @Nullable Region getTransparentRegion() {
return null;
}
/** 如果子类需要根据state来变更Drawable实例的外观，则需要重写该方法。 如果state的变更引起了Drawable实例外观变化，则返回true, 否则返回false; * Override this in your subclass to change appearance if you recognize the * specified state. * * @return Returns true if the state change has caused the appearance of * the Drawable to change (that is, it needs to be drawn), else false * if it looks the same and there is no need to redraw it since its * last state. */
protected boolean onStateChange(int[] state) {
return false;
}
/** 如果子类需要根据level来变更Drawable实例的外观，则需要重写该方法。 如果level的变更引起了Drawable实例外观变化，则返回true, 否则返回false; Override this in your subclass to change appearance if you vary based * on level. * @return Returns true if the level change has caused the appearance of * the Drawable to change (that is, it needs to be drawn), else false * if it looks the same and there is no need to redraw it since its * last level. */
protected boolean onLevelChange(int level) {
return false;
}
/** 如果子类实例需要在绘制范围发生变化后变更Drawable实例的外观，则需要重写该方法。 * Override this in your subclass to change appearance if you vary based on * the bounds. */
protected void onBoundsChange(Rect bounds) {
// Stub method.
}
/** 返回当前Drawable实例的实质宽度。 实质宽度是Drawable实例占据的宽度，包含padding值。 如果Drawable实例没有实际宽度，例如是一个颜色，则返回-1 * Returns the drawable's intrinsic width. * <p> * Intrinsic width is the width at which the drawable would like to be laid * out, including any inherent padding. If the drawable has no intrinsic * width, such as a solid color, this method returns -1. * * @return the intrinsic width, or -1 if no intrinsic width */
public int getIntrinsicWidth() {
return -1;
}
/** 返回当前Drawable实例的实质高度。 实质宽度是Drawable实例占据的高度，包含padding值。 如果Drawable实例没有实际高度，例如是一个颜色，则返回-1 * Returns the drawable's intrinsic height. * <p> * Intrinsic height is the height at which the drawable would like to be * laid out, including any inherent padding. If the drawable has no * intrinsic height, such as a solid color, this method returns -1. * * @return the intrinsic height, or -1 if no intrinsic height */
public int getIntrinsicHeight() {
return -1;
}
/** 返回当前Drawable建议的最小宽度。 如果一个View实例用当前Drawable当做背景，那么建议该View实例 宽度最小为这个值。 * Returns the minimum width suggested by this Drawable. If a View uses this * Drawable as a background, it is suggested that the View use at least this * value for its width. (There will be some scenarios where this will not be * possible.) This value should INCLUDE any padding. * * @return The minimum width suggested by this Drawable. If this Drawable * doesn't have a suggested minimum width, 0 is returned. */
public int getMinimumWidth() {
final int intrinsicWidth = getIntrinsicWidth();
return intrinsicWidth > 0 ? intrinsicWidth : 0;
}
/** 返回当前Drawable建议的最小高度。 如果一个View实例用当前Drawable当做背景，那么建议该View实例 高度最小为这个值。 * Returns the minimum height suggested by this Drawable. If a View uses this * Drawable as a background, it is suggested that the View use at least this * value for its height. (There will be some scenarios where this will not be * possible.) This value should INCLUDE any padding. * * @return The minimum height suggested by this Drawable. If this Drawable * doesn't have a suggested minimum height, 0 is returned. */
public int getMinimumHeight() {
final int intrinsicHeight = getIntrinsicHeight();
return intrinsicHeight > 0 ? intrinsicHeight : 0;
}
/** 将当前Drawable实例的padding值作为参数设置为Recti实例padding 的边界值。 如果当前实例有padding值，返回true,否则返回false； 当返回false，则Recti实例padding的边界值都设置为0； * Return in padding the insets suggested by this Drawable for placing * content inside the drawable's bounds. Positive values move toward the * center of the Drawable (set Rect.inset). * * @return true if this drawable actually has a padding, else false. When false is returned, * the padding is always set to 0. */
public boolean getPadding(@NonNull Rect padding) {
padding.set(0, 0, 0, 0);
return false;
}
/** 被隐匿 * Return in insets the layout insets suggested by this Drawable for use with alignment * operations during layout. * @hide */
public @NonNull Insets getOpticalInsets() {
return Insets.NONE;
}
/** 调用此方法获取当前Drawable实例的绘制区域轮廓。 这个方法默认被ViewOutlineProvider调用去定义View实例的轮廓。 ViewOutlineProvider：后续文章会做介绍，是个蛮有趣的类。 * Called to get the drawable to populate the Outline that defines its drawing area. * <p> * This method is called by the default {@link android.view.ViewOutlineProvider} to define * the outline of the View. * <p> * The default behavior defines the outline to be the bounding rectangle of 0 alpha. * Subclasses that wish to convey a different shape or alpha value must override this method. * * @see android.view.View#setOutlineProvider(android.view.ViewOutlineProvider) */
public void getOutline(@NonNull Outline outline) {
outline.setRect(getBounds());
outline.setAlpha(0);
}
未完待续...未完待续…
以上就是个人分析的一点结果，若有错误，请各位同学留言告知！
That’s all !
