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经历过了前面一系列的讲解，下面我们直接来看看系统里面的CheckBox与CompoundButton类的源码文件。你肯定会发现很多熟悉的地方。
结合下面源码，我们对它们进行解析解析，它里面使用的就是自定义drawable state。

我们首先直接看CheckBox的源码

public class CheckBox extends CompoundButton {public CheckBox(Context context) {this(context, null);}public CheckBox(Context context, AttributeSet attrs) {this(context, attrs, com.android.internal.R.attr.checkboxStyle);}public CheckBox(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);}@Overridepublic void onInitializeAccessibilityEvent(AccessibilityEvent event) {super.onInitializeAccessibilityEvent(event);event.setClassName(CheckBox.class.getName());}@Overridepublic void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {super.onInitializeAccessibilityNodeInfo(info);info.setClassName(CheckBox.class.getName());}
}

我们可以看到，它里面并没有做什么，因为它的操作都是继承自CompoundButton.

我们先来看看下面一个普通的布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"android:paddingBottom="@dimen/activity_vertical_margin"tools:context=".MainActivity"><CheckBoxandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="CheckBox"/></RelativeLayout>

在上面的这个相对布局中，就写了一个CheckBox，我们什么都不做，直接运行代码，就会看到下面的运行界面：

当我们单击这个CheckBox,我们发现他会被选中，那么它内部到底是怎么实现的呢？
其实使用过drawable state的人应该对这个并不陌生，我们经常这样做：

1、在res/drawable文件下创建selector.xml，示例代码如下：

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android"><item
        android:state_pressed="false"android:drawable="@drawable/title_button_back"></item><item
        android:state_pressed="true"android:drawable="@drawable/title_button_back_h"></item><item
        android:state_window_focused="false"android:drawable="@drawable/title_button_back"></item>
</selector>

2、编写布局文件，为布局文件中的ImageButton设置selector，示例代码如下：

<?xml version="1.0" encoding="utf-8"?>  
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="wrap_content" android:layout_width="fill_parent">  <ImageButton android:id="@+id/title_IB"android:layout_height="wrap_content" android:layout_width="wrap_content" android:background="#00000000" android:layout_marginRight="4dp" android:layout_centerVertical="true" android:src="@drawable/selector"></ImageButton>  
</RelativeLayout>

当我们单击这个图片按钮的时候，图片按钮的图片就会发生变化，其实CheckBox也是这样做的，只是这些系统为我们做了。

下面我们来看看系统实现源码：
上面在布局文件中直接写了一个CheckBox,布局文件被解析后就会实例化这个CheckBox对象，就会执行CheckBox的构造函数：

public CheckBox(Context context, AttributeSet attrs) {this(context, attrs, com.android.internal.R.attr.checkboxStyle);
}public CheckBox(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);
}

从上面我们可以知道两点：
1、CheckBox的默认样式是com.android.internal.R.attr.checkboxStyle
2、最终执行的时候CompoundButton的构造函数

在frameworks/base/core/res/res/values/themes.xml文件中，已经初始化了checkBoxStyle样式：

<item name="checkboxStyle">@android:style/Widget.CompoundButton.CheckBox</item>

在frameworks/base/core/res/res/values/styles.xml文件，我们来看看它的样式是什么：

<style name="Widget.CompoundButton.CheckBox"><item name="android:button">?android:attr/listChoiceIndicatorMultiple</item>
</style>

在frameworks/base/core/res/res/values/themes.xml文件：

<item name="listChoiceIndicatorMultiple">@android:drawable/btn_check</item>

可以看到，CheckBox的默认样式就是给它的button属性赋值了一个btn_check,我们来看看btn_check文件里面的具体内容。

在frameworks/base/core/res/res/drawable/btn_check.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android"><!-- Enabled states --><item android:state_checked="true" android:state_window_focused="false"android:state_enabled="true"android:drawable="@drawable/btn_check_on" /><item android:state_checked="false" android:state_window_focused="false"android:state_enabled="true"android:drawable="@drawable/btn_check_off" /><item android:state_checked="true" android:state_pressed="true"android:state_enabled="true"android:drawable="@drawable/btn_check_on_pressed" /><item android:state_checked="false" android:state_pressed="true"android:state_enabled="true"android:drawable="@drawable/btn_check_off_pressed" /><item android:state_checked="true" android:state_focused="true"android:state_enabled="true"android:drawable="@drawable/btn_check_on_selected" /><item android:state_checked="false" android:state_focused="true"android:state_enabled="true"android:drawable="@drawable/btn_check_off_selected" /><item android:state_checked="false"android:state_enabled="true"android:drawable="@drawable/btn_check_off" /><item android:state_checked="true"android:state_enabled="true"android:drawable="@drawable/btn_check_on" /><!-- Disabled states --><item android:state_checked="true" android:state_window_focused="false"android:drawable="@drawable/btn_check_on_disable" /><item android:state_checked="false" android:state_window_focused="false"android:drawable="@drawable/btn_check_off_disable" /><item android:state_checked="true" android:state_focused="true"android:drawable="@drawable/btn_check_on_disable_focused" /><item android:state_checked="false" android:state_focused="true"android:drawable="@drawable/btn_check_off_disable_focused" /><item android:state_checked="false" android:drawable="@drawable/btn_check_off_disable" /><item android:state_checked="true" android:drawable="@drawable/btn_check_on_disable" /></selector>

我们看到，state_checked为true的时候，drawable=”@drawable/btn_check_on”，state_checked为false的时候,drawable=”@drawable/btn_check_off”.
@drawable/btn_check_on图片和@drawable/btn_check_off图片，在frameworks/base/core/res/res/drawable我们可以找到：

我们可以看到，其实就是根据不同的状态，为button属性赋值了不同的图片资源，这就是我们看到的效果。

state_checked这个状态的定义，在下面进行了定义：

<declare-styleable name="DrawableStates"><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable},set when a view has input focus. --><attr name="state_focused" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable},set when a view's window has input focus. --><attr name="state_window_focused" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable},set when a view is enabled. --><attr name="state_enabled" format="boolean" /><!-- State identifier indicating that the object <var>may</var> display a check mark.See {@link R.attr#state_checked} for the identifier that indicates whether it isactually checked. --><attr name="state_checkable" format="boolean"/><!-- State identifier indicating that the object is currently checked.  See{@link R.attr#state_checkable} for an additional identifier that can indicate ifany object may ever display a check, regardless of whether state_checked iscurrently set. --><attr name="state_checked" format="boolean"/><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable},set when a view (or one of its parents) is currently selected. --><attr name="state_selected" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable},set when the user is pressing down in a view. --><attr name="state_pressed" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable},set when a view or its parent has been "activated" meaning the user has currentlymarked it as being of interest.  This is an alternative representation ofstate_checked for when the state should be propagated down the view hierarchy. --><attr name="state_activated" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable}.--><attr name="state_active" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable}.--><attr name="state_single" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable}.--><attr name="state_first" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable}.--><attr name="state_middle" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable}.--><attr name="state_last" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable},indicating that the Drawable is in a view that is hardware accelerated.This means that the device can at least render a full-screen scaledbitmap with one layer of text and bitmaps composited on top of itat 60fps.  When this is set, the colorBackgroundCacheHint will beignored even if it specifies a solid color, since that optimizationis not needed. --><attr name="state_accelerated" format="boolean" /><!-- State value for {@link android.graphics.drawable.StateListDrawable StateListDrawable},set when a pointer is hovering over the view. --><attr name="state_hovered" format="boolean" /><!-- State for {@link android.graphics.drawable.StateListDrawable StateListDrawable}indicating that the Drawable is in a view that is capable of accepting a drop ofthe content currently being manipulated in a drag-and-drop operation. --><attr name="state_drag_can_accept" format="boolean" /><!-- State for {@link android.graphics.drawable.StateListDrawable StateListDrawable}indicating that a drag operation (for which the Drawable's view is a valid recipient)is currently positioned over the Drawable. --><attr name="state_drag_hovered" format="boolean" /><!-- State for {@link android.graphics.drawable.StateListDrawable StateListDrawable}indicating that a View has accessibility focus. --><attr name="state_accessibility_focused" format="boolean" />
</declare-styleable>

我们可以看到<attr name="state_checked" format="boolean"/>

下面我们看看CompoundButton的构造函数，因为CheckBox最终执行的是它的构造函数。

public CompoundButton(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);TypedArray a =context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.CompoundButton, defStyle, 0);Drawable d = a.getDrawable(com.android.internal.R.styleable.CompoundButton_button);if (d != null) {setButtonDrawable(d);}boolean checked = a.getBoolean(com.android.internal.R.styleable.CompoundButton_checked, false);setChecked(checked);a.recycle();
}

我们可以知道CompoundButton自定义了两个属性，进入frameworks/base/core/res/res/values/attrs.xml文件：

<declare-styleable name="CompoundButton"><!-- Indicates the initial checked state of this button. --><attr name="checked" format="boolean" /><!-- Drawable used for the button graphic (e.g. checkbox, radio button, etc). --><attr name="button" format="reference"/>
</declare-styleable>

我们可以看到它定义了两个属性：checked，button，一个存放的是一个boolean类型的值，表示是否被选中，一个存放的是引用类型，对应的是一个图片。
在构造函数中，我们获取到了这两个属性值。上面就是对button这个属性进行了默认赋值，然后我们这里就可以获取到上面的btn_check这个xml文件的drawable。
也就是说Drawable d = a.getDrawable(com.android.internal.R.styleable.CompoundButton_button)中的d的到的就是btn_check这个xml文件的drawable。

然后分别调用了setButtonDrawable(d)和setChecked(checked)来对我们自定义的控件进行了设置。

我们来看看setButtonDrawable(d)函数：

public void setButtonDrawable(Drawable d) {if (d != null) {if (mButtonDrawable != null) {mButtonDrawable.setCallback(null);unscheduleDrawable(mButtonDrawable);}//这里设置Callback的原因就是refreshDrawableState刷新的时候可以回调到invalidateDrawable//这样就可以重绘，这个我们在#详解refreshDrawableList()的执行流程#这篇文件讲过d.setCallback(this);d.setVisible(getVisibility() == VISIBLE, false);mButtonDrawable = d;setMinHeight(mButtonDrawable.getIntrinsicHeight());}refreshDrawableState();
}

最后调用了refreshDrawableState这个方法，这个执行过程我们也分析过，整个执行思路都是一样，不过不同的是，里面的很多方法都被覆盖了。

这里我们再来把整个思路走一走。

refreshDrawableState执行的还是View里面的这个方法，直接看源码。

public void refreshDrawableState() {//首先把标志设置为PFLAG_DRAWABLE_STATE_DIRTYmPrivateFlags |= PFLAG_DRAWABLE_STATE_DIRTY;drawableStateChanged();ViewParent parent = mParent;if (parent != null) {parent.childDrawableStateChanged(this);}
}

drawableStateChanged这个方法不在执行View里面的这个方法，因为CompoundButton里面有这个方法，我们看看CompoundButton的这个方法。

@Override
protected void drawableStateChanged() {super.drawableStateChanged();if (mButtonDrawable != null) {int[] myDrawableState = getDrawableState();// Set the state of the DrawablemButtonDrawable.setState(myDrawableState);invalidate();}
}

getDrawableState这个函数还是调用的View的这个函数。

public final int[] getDrawableState() {//PFLAG_DRAWABLE_STATE_DIRTY是前面refreshDrawableState设置的//如果mDrawableState不为空，并且不需要刷新状态，则直接返回，否则重新进行获取if ((mDrawableState != null) && ((mPrivateFlags & PFLAG_DRAWABLE_STATE_DIRTY) == 0)) {return mDrawableState;} else {//这里就是重新得到视图状态，并将其返回mDrawableState = onCreateDrawableState(0);//清除前面refreshDrawableState设置的标识mPrivateFlags &= ~PFLAG_DRAWABLE_STATE_DIRTY;return mDrawableState;}
}

下面调用到了onCreateDrawableState这个方法，这个方法也不在是执行View里面的这个方法，因为CompoundButton里面也有这个方法。

@Override
protected int[] onCreateDrawableState(int extraSpace) {final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);if (isChecked()) {mergeDrawableStates(drawableState, CHECKED_STATE_SET);}return drawableState;
}

结合之前我们详解refreshDrawableList()的执行流程的分析。这个方法就是在之前的基础上加入了一个判断，如果isChekced为真，就把我们自定义的这个状态加进去，这样当前状态里面就有我们的自定义的状态，后面在状态二维数组中查询的时候，就可以找到对应的drawable图片进行设置了。

这个函数执行完了就会回到上面的getDrawableState函数，然后把当前的状态返回到drawableStateChanged函数中，接着看里面的代码。

接着执行mButtonDrawable.setState(myDrawableState)，把得到的当前状态数组设置进去。里面的执行过去前面详解refreshDrawableList()的执行流程的分析也说过，是完全一样的，我们就省略,不明白就再看看，最后会执行invalidateSelf函数。

这个函数就会得到前面我们设置的Callback回调，调用它的invalidateDrawable方法。

public void invalidateSelf() {final Callback callback = getCallback();if (callback != null) {callback.invalidateDrawable(this);}
}

跟前面一样，因为View实现了这个回调，所以它执行的是View里面的实现方法。在这个方法里面执行了invalidate函数，所以会执行onDraw方法.
在CompoundButton里面实现了这个方法，它不再直接执行View里面的这个方法了。

protected void onDraw(Canvas canvas) {super.onDraw(canvas);final Drawable buttonDrawable = mButtonDrawable;if (buttonDrawable != null) {final int verticalGravity = getGravity() & Gravity.VERTICAL_GRAVITY_MASK;final int drawableHeight = buttonDrawable.getIntrinsicHeight();final int drawableWidth = buttonDrawable.getIntrinsicWidth();int top = 0;switch (verticalGravity) {case Gravity.BOTTOM:top = getHeight() - drawableHeight;break;case Gravity.CENTER_VERTICAL:top = (getHeight() - drawableHeight) / 2;break;}int bottom = top + drawableHeight;int left = isLayoutRtl() ? getWidth() - drawableWidth : 0;int right = isLayoutRtl() ? getWidth() : drawableWidth;buttonDrawable.setBounds(left, top, right, bottom);buttonDrawable.draw(canvas);}
}

这样这个图片就绘制出来了，从btn_check里面我们可以看到最开始显示的图片是btn_check_off，当我们单击这个CheckBox的时候，会执行performClick函数。

@Override
public boolean performClick() {/** XXX: These are tiny, need some surrounding 'expanded touch area',* which will need to be implemented in Button if we only override* performClick()*//* When clicked, toggle the state */toggle();return super.performClick();
}

接着执行toggle函数。

public void toggle() {setChecked(!mChecked);
}

这里面就把当前的状态设置为与之前相反的状态，刚开始为false,这个时候就为true.

接着我们看看setChecked函数。

public void setChecked(boolean checked) {if (mChecked != checked) {mChecked = checked;refreshDrawableState();notifyViewAccessibilityStateChangedIfNeeded(AccessibilityEvent.CONTENT_CHANGE_TYPE_UNDEFINED);// Avoid infinite recursions if setChecked() is called from a listenerif (mBroadcasting) {return;}mBroadcasting = true;if (mOnCheckedChangeListener != null) {mOnCheckedChangeListener.onCheckedChanged(this, mChecked);}if (mOnCheckedChangeWidgetListener != null) {mOnCheckedChangeWidgetListener.onCheckedChanged(this, mChecked);}mBroadcasting = false;            }
}

在这个里面又执行了refreshDrawableState函数，同样把上面的refreshDrawableState过程又执行了一遍，执行在到onCreateDrawableState就不一样了。
我们在来看看这个函数：

protected int[] onCreateDrawableState(int extraSpace) {final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);if (isChecked()) {mergeDrawableStates(drawableState, CHECKED_STATE_SET);}return drawableState;
}

第一次执行的时候isChecked为false,自定义的这个状态没有合进去，这次就把自定义的这个状态合进去，这样就可以查询到我们的状态，所以就可以找到定义的drawable,所以图片发生改变为btn_check_on。

最后把完整的CompoundButton源码贴出来，可以对照上面将的，然后再根据前面讲的详解refreshDrawableList()的执行流程这个过程理解理解。

/** Copyright (C) 2007 The Android Open Source Project** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at**      http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/package android.widget;import com.android.internal.R;import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.ViewDebug;
import android.view.accessibility.AccessibilityEvent;
import android.view.accessibility.AccessibilityNodeInfo;/*** <p>* A button with two states, checked and unchecked. When the button is pressed* or clicked, the state changes automatically.* </p>** <p><strong>XML attributes</strong></p>* <p>* See {@link android.R.styleable#CompoundButton* CompoundButton Attributes}, {@link android.R.styleable#Button Button* Attributes}, {@link android.R.styleable#TextView TextView Attributes}, {@link* android.R.styleable#View View Attributes}* </p>*/
public abstract class CompoundButton extends Button implements Checkable {private boolean mChecked;private int mButtonResource;private boolean mBroadcasting;private Drawable mButtonDrawable;private OnCheckedChangeListener mOnCheckedChangeListener;private OnCheckedChangeListener mOnCheckedChangeWidgetListener;private static final int[] CHECKED_STATE_SET = {R.attr.state_checked};public CompoundButton(Context context) {this(context, null);}public CompoundButton(Context context, AttributeSet attrs) {this(context, attrs, 0);}public CompoundButton(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);TypedArray a =context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.CompoundButton, defStyle, 0);Drawable d = a.getDrawable(com.android.internal.R.styleable.CompoundButton_button);if (d != null) {setButtonDrawable(d);}boolean checked = a.getBoolean(com.android.internal.R.styleable.CompoundButton_checked, false);setChecked(checked);a.recycle();}public void toggle() {setChecked(!mChecked);}@Overridepublic boolean performClick() {/** XXX: These are tiny, need some surrounding 'expanded touch area',* which will need to be implemented in Button if we only override* performClick()*//* When clicked, toggle the state */toggle();return super.performClick();}@ViewDebug.ExportedPropertypublic boolean isChecked() {return mChecked;}/*** <p>Changes the checked state of this button.</p>** @param checked true to check the button, false to uncheck it*/public void setChecked(boolean checked) {if (mChecked != checked) {mChecked = checked;refreshDrawableState();notifyViewAccessibilityStateChangedIfNeeded(AccessibilityEvent.CONTENT_CHANGE_TYPE_UNDEFINED);// Avoid infinite recursions if setChecked() is called from a listenerif (mBroadcasting) {return;}mBroadcasting = true;if (mOnCheckedChangeListener != null) {mOnCheckedChangeListener.onCheckedChanged(this, mChecked);}if (mOnCheckedChangeWidgetListener != null) {mOnCheckedChangeWidgetListener.onCheckedChanged(this, mChecked);}mBroadcasting = false;            }}/*** Register a callback to be invoked when the checked state of this button* changes.** @param listener the callback to call on checked state change*/public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {mOnCheckedChangeListener = listener;}/*** Register a callback to be invoked when the checked state of this button* changes. This callback is used for internal purpose only.** @param listener the callback to call on checked state change* @hide*/void setOnCheckedChangeWidgetListener(OnCheckedChangeListener listener) {mOnCheckedChangeWidgetListener = listener;}/*** Interface definition for a callback to be invoked when the checked state* of a compound button changed.*/public static interface OnCheckedChangeListener {/*** Called when the checked state of a compound button has changed.** @param buttonView The compound button view whose state has changed.* @param isChecked  The new checked state of buttonView.*/void onCheckedChanged(CompoundButton buttonView, boolean isChecked);}/*** Set the background to a given Drawable, identified by its resource id.** @param resid the resource id of the drawable to use as the background */public void setButtonDrawable(int resid) {if (resid != 0 && resid == mButtonResource) {return;}mButtonResource = resid;Drawable d = null;if (mButtonResource != 0) {d = getResources().getDrawable(mButtonResource);}setButtonDrawable(d);}/*** Set the background to a given Drawable** @param d The Drawable to use as the background*/public void setButtonDrawable(Drawable d) {if (d != null) {if (mButtonDrawable != null) {mButtonDrawable.setCallback(null);unscheduleDrawable(mButtonDrawable);}d.setCallback(this);d.setVisible(getVisibility() == VISIBLE, false);mButtonDrawable = d;setMinHeight(mButtonDrawable.getIntrinsicHeight());}refreshDrawableState();}@Overridepublic void onInitializeAccessibilityEvent(AccessibilityEvent event) {super.onInitializeAccessibilityEvent(event);event.setClassName(CompoundButton.class.getName());event.setChecked(mChecked);}@Overridepublic void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {super.onInitializeAccessibilityNodeInfo(info);info.setClassName(CompoundButton.class.getName());info.setCheckable(true);info.setChecked(mChecked);}@Overridepublic int getCompoundPaddingLeft() {int padding = super.getCompoundPaddingLeft();if (!isLayoutRtl()) {final Drawable buttonDrawable = mButtonDrawable;if (buttonDrawable != null) {padding += buttonDrawable.getIntrinsicWidth();}}return padding;}@Overridepublic int getCompoundPaddingRight() {int padding = super.getCompoundPaddingRight();if (isLayoutRtl()) {final Drawable buttonDrawable = mButtonDrawable;if (buttonDrawable != null) {padding += buttonDrawable.getIntrinsicWidth();}}return padding;}/*** @hide*/@Overridepublic int getHorizontalOffsetForDrawables() {final Drawable buttonDrawable = mButtonDrawable;return (buttonDrawable != null) ? buttonDrawable.getIntrinsicWidth() : 0;}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);final Drawable buttonDrawable = mButtonDrawable;if (buttonDrawable != null) {final int verticalGravity = getGravity() & Gravity.VERTICAL_GRAVITY_MASK;final int drawableHeight = buttonDrawable.getIntrinsicHeight();final int drawableWidth = buttonDrawable.getIntrinsicWidth();int top = 0;switch (verticalGravity) {case Gravity.BOTTOM:top = getHeight() - drawableHeight;break;case Gravity.CENTER_VERTICAL:top = (getHeight() - drawableHeight) / 2;break;}int bottom = top + drawableHeight;int left = isLayoutRtl() ? getWidth() - drawableWidth : 0;int right = isLayoutRtl() ? getWidth() : drawableWidth;buttonDrawable.setBounds(left, top, right, bottom);buttonDrawable.draw(canvas);}}@Overrideprotected int[] onCreateDrawableState(int extraSpace) {final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);if (isChecked()) {mergeDrawableStates(drawableState, CHECKED_STATE_SET);}return drawableState;}@Overrideprotected void drawableStateChanged() {super.drawableStateChanged();if (mButtonDrawable != null) {int[] myDrawableState = getDrawableState();// Set the state of the DrawablemButtonDrawable.setState(myDrawableState);invalidate();}}@Overrideprotected boolean verifyDrawable(Drawable who) {return super.verifyDrawable(who) || who == mButtonDrawable;}@Overridepublic void jumpDrawablesToCurrentState() {super.jumpDrawablesToCurrentState();if (mButtonDrawable != null) mButtonDrawable.jumpToCurrentState();}static class SavedState extends BaseSavedState {boolean checked;/*** Constructor called from {@link CompoundButton#onSaveInstanceState()}*/SavedState(Parcelable superState) {super(superState);}/*** Constructor called from {@link #CREATOR}*/private SavedState(Parcel in) {super(in);checked = (Boolean)in.readValue(null);}@Overridepublic void writeToParcel(Parcel out, int flags) {super.writeToParcel(out, flags);out.writeValue(checked);}@Overridepublic String toString() {return "CompoundButton.SavedState{"+ Integer.toHexString(System.identityHashCode(this))+ " checked=" + checked + "}";}public static final Parcelable.Creator<SavedState> CREATOR= new Parcelable.Creator<SavedState>() {public SavedState createFromParcel(Parcel in) {return new SavedState(in);}public SavedState[] newArray(int size) {return new SavedState[size];}};}@Overridepublic Parcelable onSaveInstanceState() {// Force our ancestor class to save its statesetFreezesText(true);Parcelable superState = super.onSaveInstanceState();SavedState ss = new SavedState(superState);ss.checked = isChecked();return ss;}@Overridepublic void onRestoreInstanceState(Parcelable state) {SavedState ss = (SavedState) state;super.onRestoreInstanceState(ss.getSuperState());setChecked(ss.checked);requestLayout();}
}