Android Drawable徹底解析（一）：Drawable源碼分析（上） Android Drawable徹底解析（一）：Drawable源碼分析（中） Android Drawable徹底解析（一）：Drawable源碼分析（下）java
呃...我不是故意要湊篇幅寫個什麼上下篇，實在是由於Drawable源碼有點長，一篇寫不下啦O(∩_∩)O~android
上一篇文章 其實你不懂：Drawable着色(tint)的兼容方案 源碼解析 描述了Drawable的着色原理，文章裏有涉及到Drawable的一些方法，順便看一下Drawabld的源碼，發現Drawable涉及的面很廣，尤爲是居然有那麼多的繼承類。想一想本身平時也就用過ColorDrawable,StateListDrawable,BitmapDrawable頗有限的幾個子類，對於Drawable的應用仍是太零散了，因此寫這個Drawable系列文章，對其作一個相對完整的分析！ios
這是「Drawable徹底解析」系列文章的第一篇，就從Drawable的源碼分析開始！ ####1:Drawable與其子類的繼承關係 直接看圖，暫不詳細介紹具體使用方法。 
能夠看到Drawable居然有這麼多子類，真的須要花一些時間才能分別搞得清楚。 ####2:Drawable源碼分析/翻譯 此處源碼是SDK 24版本下的Drawable.java文件，不一樣版本下應該會有出入，敬請注意！ 源碼較長，英文較好的同窗記得指出我翻譯和理解的錯誤！canvas
package android.graphics.drawable;
import com.android.internal.R;
*****略
/**
Drawable是一個用於處理各類可繪製資源的抽象類。咱們使用Drawable最多見的狀況就是將獲取到的資源繪製到屏幕上；Drawable類提供了一些通用的API來處理如下具備多種表現形式的可視資源/視覺資源。
* 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不一樣，Drawable實例不具有任何能力接收事件或與用戶交互。
* Unlike a {@link android.view.View}, a Drawable does not have any facility to
* receive events or otherwise interact with the user.
*
除了簡單繪圖，Drawable提供了一些通用的機制使客戶端與當前正在繪製的內容進行交互。
* <p>In addition to simple drawing, Drawable provides a number of generic
* mechanisms for its client to interact with what is being drawn:
*
setBounds方法必須被Drawable實例調用，用於聲明Drawable實例繪製的位置和大小。全部的Drawable實例都會生成請求的尺寸，這一點一般能夠經過縮放圖像很容易就達到。對一些Drawable實例，客戶端能夠經過調用getIntrinsicHeight和getIntrinsicWidth方法獲得其首選尺寸。
* <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會將Drawable實例與實例中內容的間隔信息存儲在Rect實例中。
* <li> The {@link #getPadding} method can return from some Drawables
* information about how to frame content that is placed inside of them.
例如，一個Drawable實例做爲一個Button的背景，Button控件實例須要返回padding值用來放置Button控件顯示的內容。
* 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方法容許客戶端告知Drawable實例在什麼狀態下才進行繪製。
例如「焦點獲取狀態」，「選中狀態」等等。某些Drawable可能會根據選定的狀態值變動它們的外觀。
* <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方法容許客戶端提供一個單一的連續控制器來編輯正在顯示的Drawable實例，例如電量水平或者進度值。某些Drawable實例能夠根據當前的level值變動它們的外觀。
* <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.
*
經過Callback接口，一個Drawable實例能夠回調其客戶端來執行動畫。爲了動畫能夠被執行，全部的客戶端都應該支持這個Callback接口。實現這一效果最簡單的方法就是經過系統提供的機制，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>
*
儘管一般狀況下對應用不可見，Drawable實例可能存在如下多種形式：
Bitmap:最簡單的Drawable形式，PNG或者JPEG圖片。
.9圖：PNG的一個擴展，能夠支持設置其如何填充內容，如何被拉伸。
Shape：包含簡單的繪製指令，用於替代bitmap，某些狀況下對大小調整有更好表現。
Layers：一個複合的Drawable，按照層級進行繪製，單個Drawable實例繪製於其下層Drawable實例集合之上。
States：一個複合的Drawable，根據它的state選擇一個Drawable集合。
Levels：一個複合的Drawable，根據它的level選擇一個Drawable集合。
Scale：一個複合的Drawable和單個Drawable實例構成，它的整體尺寸由它的當前level值決定。
* 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>
*
自定義Drawable
全部的Android版本都支持框架層提供的Drawable類被擴展/自定義和應用於運行時。從Android版本24開始，自定義Drawable能夠在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：
自定義Drawable僅能應用於當前應用，其餘應用沒法加載它們。
自定義Drawable必須繼承Drawable類，至少重寫draw方法以繪製內容。
* <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.
自定義Drawable用於XML中有多種方式：
1：直接引用自定義Drawable類名的全稱，且該類必須爲公共頂層類。
2：使用drawable做爲XML的元素名稱，指定該自定義Drawable類的全稱。該自定義Drawable類能夠是 公共頂層類或者公共靜態內部類。
* <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;
/**
在經過setBounds設置的範圍內進行繪製，經過調用setAlpha和setColorFilter
等方法能夠影響繪製的效果。
canvas：當前Drawable實例要被繪製到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);
/**
爲當前Drawable實例設置一個矩形範圍，在draw方法調用時候，
Drawable實例將被繪製到這個矩形範圍內。
* 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);
}
/**
將當前Drawable實例經過setBounds設置的繪製範圍拷貝到客戶端提供的Rect實例中返回
* 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);
}
/**
返回當前Drawable實例的矩形繪製範圍。注：返回的矩形就是
當前Drawable實際的繪製範圍矩形，因此若是是須要一個拷貝的矩形範圍，
應該調用copyBounds來代替。
調用getBounds，你不能修改返回的矩形，會影響Drawable實例。
* 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;
}
/**
返回當前Drawable實例的模糊繪製範圍矩形。
注：返回的矩形和當前Drawable繪製返回矩形是同一個對象。
* 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();
}
/**
這段我沒怎麼看懂，勉強翻譯一下，哪位同窗懂能夠留言！
爲配置參數設置一個標記，當該配置參數變動時可能改變當前
Drawable實例，要求當前Drawable實例從新建立。
* 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;
}
/**
當設置爲true，該Drawable實例在繪製到一個低於8-bits每單位色值
的設備上時候顏色將發生‘抖動’？
* 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) {}
/**
當設置爲true,則該Drawable實例在縮放或者旋轉時候將
對它關聯的bitmap進行濾波過濾。能夠提高旋轉時的繪製效果。
若是該Drawable實例未使用bitmap,這個方法無做用。
* 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;
}
/**
一個回調接口，用於調度和執行Drawable實例的動畫。
若是要實現自定義的動畫Drawable,就須要實現這個接口。
* 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實例被重繪時候調用。在當前Drawable實例位置的View
實例須要重繪，或者至少部分重繪。
* 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);
/**
一個Drawable實例能夠調用這個方法預先安排動畫的下一幀。
也能夠經過Handler.postAtTime實現。
* 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);
/**
一個Drawable實例能夠調用這個方法取消以前安排的某一幀。
也能夠經過Handler.removeCallbacks實現。
* 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);
}
/**
若是客戶端要求支持動畫Drawable,將一個Callback實例綁定到當前
Drawable實例上。
* 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;
}
/**
經過由調用setCallBack設置過的Callback實例執行
invalidateDrawable。若是沒有調用過setCallback，則無效果
* 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);
}
}
/**
經過由調用setCallBack設置過的Callback實例執行
scheduleDrawable。若是沒有調用過setCallback，則無效果
* 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);
}
}
/**
經過由調用setCallBack設置過的Callback實例執行
unscheduleDrawable。若是沒有調用過setCallback，則無效果
* 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);
}
}
/**
獲取當前Drawable實例的佈局方向。
* 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;
}
/**
設置當前Drawable實例的佈局方向。
* 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) {
//若是當前Drawable佈局方向和layoutDirection不一致，
//則修改佈局方向爲layoutDirection，而後執行onLayoutDirectionChanged
mLayoutDirection = layoutDirection;
return onLayoutDirectionChanged(layoutDirection);
}
return false;
}
/**
當調用setLayoutDirection方法，Drawable佈局方向發生變化後調用
* 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;
}
/**
設置Drawable實例的透明度。
0：徹底透明
255:徹底不透明
* 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;
}
/**
被隱匿
* @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!
}
/**
爲當前Drawable實例設置顏色濾鏡
* 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);
/**
爲當前Drawable實例設置濾鏡效果
* 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));
}
/**
爲當前Drawable實例着色
* Specifies tint color for this drawable.
* <p>
當前Drawable實例的繪製內容在被繪製到屏幕上以前將被指定顏色着色
當前方法和setColorFilter相似。
* 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));
}
/**
根據ColorStateList對當前Drawable實例進行着色
這個一個空方法！！！在上一篇文章中已經指出，Drawabld的子類
實現了這個方法。
* 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) {}
/**
設置當前Drawable實例着色的過濾模式
* 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;
}
/**
取消當前Drawable實例的濾鏡。
* Removes the color filter for this drawable.
*/
public void clearColorFilter() {
setColorFilter(null);
}
/**
設置當前Drawable實例熱點區域的中心點座標
* 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) {}
/**
設置當前Drawable實例的熱點區域的邊界
* 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());
}
/**
被隱匿
* Whether this drawable requests projection.
*
* @hide magic!
*/
public boolean isProjected() {
return false;
}
/**
標示當前Drawable實例的外觀是否要根據state進行變動。
客戶端能夠用這個方法判斷是否有必要計算state並調用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;
}
/**
爲當前Drawable實例設置一個狀態值集合。當現有狀態和stateSet
不一樣時候，觸發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;
}
/**
若是當前Drawable實例在執行過渡動畫，要求當前實例
當即跳轉到當前狀態並跳過任何正在執行的動畫。
* 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() {
}
/**
返回當前Drawable實例正在使用的Drawable實例，
對於通常單個Drawable，返回值就是自身，對於像StateListDrawable
這樣的複合Drawable實例，則返回其持有的一個子Drawable實例。
* @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;
}
/**
爲當前Drawable實例設置圖像級別，從0到10000。setLevel使得
Drawable實例能夠經過一個不斷變化的控制器來變動它的圖像，
例如音量等級或者進度。
* 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) {
//修改圖像等級爲level，並調用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;
}
~~~~(>_<)~~~~
當前文章長度正在接近簡書的限度，請考慮分篇書寫吧
~~~~(>_<)~~~~
/**
設置當前Drawable實例是否可見，並不會影響Drawable實例的行爲，
可是能夠被某些Drawable來控制是否執行動畫。
例如：AnimationDrawable能夠經過這個方法啓動或者中止動畫，
後續文章會有驗證。
* 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;
}
/**
設置當前Drawable實例是否是自動被「鏡像」/左右對調
當它的佈局模式是從右到左
* 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;
}
/**
爲當前Drawable實例和它的子實例應用指定的主題
* 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子類會作自定義實現
}
public boolean canApplyTheme() {
return false;
}
/**
返回當前Drawable實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}-徹底透明
{@link android.graphics.PixelFormat#OPAQUE}-徹底不透明
若是Drawable中的內容可見性不肯定，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();
/**
根據兩個不透明度值，返回合適的值。
兩個不透明度值若相等，直接返回；
不然若是兩個透明度值有至少一個是UNKNOWN，返回UNKNOWN；
不然若是兩個透明度值有至少一個是TRANSLUCENT，返回TRANSLUCENT；
不然若是兩個透明度值有至少一個是TRANSPARENT，返回TRANSPARENT；
不然返回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;
}
/**
返回在當前Drawable實例中徹底透明的一個區域。
這個區域能夠用來影響繪製操做，定義當前Drawable實例的目標
在渲染當前Drawable實例時候哪一個區域不須要改變。
* 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;
}
/**
若是子類須要根據state來變動Drawable實例的外觀，則須要重寫該方法。
若是state的變動引發了Drawable實例外觀變化，則返回true,
不然返回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;
}
/**
若是子類須要根據level來變動Drawable實例的外觀，則須要重寫該方法。
若是level的變動引發了Drawable實例外觀變化，則返回true,
不然返回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;
}
/**
若是子類實例須要在繪製範圍發生變化後變動Drawable實例的外觀，則須要重寫該方法。
* Override this in your subclass to change appearance if you vary based on
* the bounds.
*/
protected void onBoundsChange(Rect bounds) {
// Stub method.
}
/**
返回當前Drawable實例的實質寬度。
實質寬度是Drawable實例佔據的寬度，包含padding值。
若是Drawable實例沒有實際寬度，例如是一個顏色，則返回-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;
}
/**
返回當前Drawable實例的實質高度。
實質寬度是Drawable實例佔據的高度，包含padding值。
若是Drawable實例沒有實際高度，例如是一個顏色，則返回-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;
}
/**
返回當前Drawable建議的最小寬度。
若是一個View實例用當前Drawable當作背景，那麼建議該View實例
寬度最小爲這個值。
* 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;
}
/**
返回當前Drawable建議的最小高度。
若是一個View實例用當前Drawable當作背景，那麼建議該View實例
高度最小爲這個值。
* 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;
}
/**
將當前Drawable實例的padding值做爲參數設置爲Recti實例padding
的邊界值。
若是當前實例有padding值，返回true,不然返回false；
當返回false，則Recti實例padding的邊界值都設置爲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;
}
/**
被隱匿
* 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;
}
/**
調用此方法獲取當前Drawable實例的繪製區域輪廓。
這個方法默認被ViewOutlineProvider調用去定義View實例的輪廓。
ViewOutlineProvider：後續文章會作介紹，是個蠻有趣的類。
* 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);
}
未完待續...
未完待續...安全
以上就是我的分析的一點結果，如有錯誤，請各位同窗留言告知！app
That's all !框架