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。 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。
* 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。
*
* - The {@link #setBounds} method must 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。
*
- 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。
*
- 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。
*
- 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。
*
- 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}.
*
*
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:
*
*
* - Bitmap: the simplest Drawable, a PNG or JPEG image.
*
- Nine Patch: an extension to the PNG format allows it to
* specify information about how to stretch it and place things inside of
* it.
*
- Shape: contains simple drawing commands instead of a raw
* bitmap, allowing it to resize better in some cases.
*
- Layers: a compound drawable, which draws multiple underlying
* drawables on top of each other.
*
- States: a compound drawable that selects one of a set of
* drawables based on its state.
*
- Levels: a compound drawable that selects one of a set of
* drawables based on its level.
*
- Scale: a compound drawable with a single child drawable,
* whose overall size is modified based on the current level.
*
*
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。
*
* Custom drawables
*
*
* 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.
*
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。
* Note: Custom drawable classes are only accessible from
* within your application package. Other applications will not be able to load
* them.
*
* 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。
*
* Custom drawables classes may be used in XML in multiple ways:
*
* -
* 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.
*
*
*
* -
* Using drawable as the XML element name and specifying the
* fully-qualified class name from the class attribute. This
* method may be used for both public top-level classes and public
* static inner classes.
*
*
*
*
*
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 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).
*
* 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.
*
*
This can improve appearance when bitmaps are rotated. If the drawable
* does not use bitmaps, this call is ignored.
*
* @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 (what, who, when) 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 (what, who) 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.
*
* 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.
*
*
* Pass {@code null} to remove any existing color filter.
*
* Note: Setting a non-{@code null} color
* filter disables {@link #setTintList(ColorStateList) tint}.
*
*
* @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.
*
* Convenience for {@link #setColorFilter(ColorFilter)} which constructs a
* {@link PorterDuffColorFilter}.
*
* Note: Setting a color filter disables
* {@link #setTintList(ColorStateList) tint}.
*
*/
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.
*
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)}.
*
*
* To clear the tint, pass {@code null} to
* {@link #setTintList(ColorStateList)}.
*
* Note: Setting a color filter via
* {@link #setColorFilter(ColorFilter)} or
* {@link #setColorFilter(int, PorterDuff.Mode)} overrides tint.
*
*
* @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.
*
* 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)}.
*
* Note: Setting a color filter via
* {@link #setColorFilter(ColorFilter)} or
* {@link #setColorFilter(int, PorterDuff.Mode)} overrides tint.
*
*
* @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.
*
* 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}.
*
* Note: Setting a color filter via
* {@link #setColorFilter(ColorFilter)} or
* {@link #setColorFilter(int, PorterDuff.Mode)} overrides tint.
*
*
* @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}].
*
* 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, and
* true will be returned from this function.
*
*
Note: The Drawable holds a reference on to stateSet
* until a new state array is given to it, so you must not modify this
* array during that time.
*
* @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.
*
* 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, and
* 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;
}
~~~~(>_<)~~~~
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}.
*
*
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.
*
*
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.
*
*
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.
*
*
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.
*
* 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.
*
* 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.
*
* This method is called by the default {@link android.view.ViewOutlineProvider} to define
* the outline of the View.
*
* 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 !
转载于:https://my.oschina.net/u/3045680/blog/854473