android4.0新控件Switch方法解析

        就是很像開關的那種控件，它隻有兩個狀态：on和off：在IOS中，有個UISwitch控件，其效果圖，如下：

在android4.0裡面，添加了一個和這個類似的控件：Switch，很形象，開關。效果圖如下：

其類關系圖如下：

java.lang.Object
↳	android.view.View
↳	android.widget.TextView
↳	android.widget.Button
↳	android.widget.CompoundButton
↳	android.widget.Switch

父類：compoundButton。

類的概述：

    Switch是一個可以在兩種狀态切換的開關控件。使用者可以拖動"thumb"來回選擇，也可以像選擇複選框一樣點選切換Switch的狀态。

主要方法：

Public Methods
int	getCompoundPaddingRight() Returns the right padding of the view, plus space for the right Drawable if any.
CharSequence	getTextOff() Returns the text displayed when the button is not in the checked state.
CharSequence	getTextOn() Returns the text displayed when the button is in the checked state.
void	jumpDrawablesToCurrentState() Call  Drawable.jumpToCurrentState()  on all Drawable objects associated with this view.
void	onMeasure(int widthMeasureSpec, int heightMeasureSpec) Measure the view and its content to determine the measured width and the measured height.
void	onPopulateAccessibilityEvent( AccessibilityEvent event) Called from  dispatchPopulateAccessibilityEvent(AccessibilityEvent)  giving a chance to this View to populate the accessibility event with its text content.
boolean	onTouchEvent( MotionEvent ev) Implement this method to handle touch screen motion events.
void	setChecked(boolean checked) Changes the checked state of this button.
void	setSwitchTextAppearance( Context context, int resid) Sets the switch text color, size, style, hint color, and highlight color from the specified TextAppearance resource.
void	setSwitchTypeface( Typeface tf, int style) Sets the typeface and style in which the text should be displayed on the switch, and turns on the fake bold and italic bits in the Paint if the Typeface that you provided does not have all the bits in the style that you specified.
void	setSwitchTypeface( Typeface tf) Sets the typeface in which the text should be displayed on the switch.
void	setTextOff( CharSequence textOff) Sets the text displayed when the button is not in the checked state.
void	setTextOn( CharSequence textOn) Sets the text displayed when the button is in the checked state.

getCompoundPaddingRight():沒弄清楚什麼意思。

在TextView中的源碼：

public int getCompoundDrawablePadding() {
        final Drawables dr = mDrawables;
        return dr != null ? dr.mDrawablePadding : 0;
    }
           

jumpDrawableToCurrentState():在與Switch相關的Drawable操作時調用 Drawable.jumpToCurrentState()這個方法。

     getTextOff()、getTextOn()、 setTextOff()、setTextOn()這四個方法比較簡單，就是設定和擷取非選中和選中狀态下的文本值。

     onMeasure():測量控件寬高，供繪圖時使用。

     onTouchEvent（MotionEvent ev）實作這一方法傳遞觸摸屏運動事件。

setChecked()設定Switch的狀态（選中，非選中）

setSwitchTextAppearance()設定字型大小

setSwitchTextTypefaces設定字型格式

看看google官方在/frameworks/base/core/res/res/values/styles.xml的一個定義：

<style name="Widget.Holo.CompoundButton.Switch">
        <item name="android:track">@android:drawable/switch_track_holo_dark</item>
        <item name="android:thumb">@android:drawable/switch_inner_holo_dark</item>
        <item name="android:switchTextAppearance">@android:style/TextAppearance.Holo.Widget.Switch</item>
        <item name="android:textOn">@android:string/capital_on</item>
        <item name="android:textOff">@android:string/capital_off</item>
        <item name="android:thumbTextPadding">12dip</item>
        <item name="android:switchMinWidth">96dip</item>
        <item name="android:switchPadding">16dip</item>
    </style>
           

可以在main.xml中這樣定義：

<Switch 
        android:id="@+id/demo_switch"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView"
        android:textOn="開"
        android:textOff="關"
        />
           

當Switch狀态切換時：

mSwitch.setOnCheckedChangeListener(new OnCheckedChangeListener() {
			
			@Override
			public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
				if(isChecked) {
					//選中時 do some thing 
					statusText.setText("開");
				} else {
					//非選中時 do some thing 
					statusText.setText("關");
				}
				
			}
		});
           

基本上先簡單的講到這。