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Andorid

Andorid-foreground 解析

---

foreground 前景色

　　foreground 也就是前景色，它与background相对应，顾名思义，它指定的drawable是在view视图的上方绘制的。

开发实例

1.实现遮罩层：

<FrameLayout
        android:id="@+id/id_frameLayout"android:layout_width="wrap_content"android:layout_height="wrap_content"android:foreground="#aaff0000"android:foregroundTintMode="src_in"><TextView
            android:id="@+id/id_text"android:layout_width="100dp"android:layout_height="100dp"android:text="NO.1"android:gravity="center_horizontal|center_vertical"/></FrameLayout>

实现效果
2.实现点击效果
　　属性能设置为drawable，我们自然就想到了也可以使用 selector drawable，在点击时套上drawable来实现类似点击效果的功能

xml代码:

    <FrameLayout
        android:id="@+id/id_frameLayout"android:layout_width="wrap_content"android:layout_height="wrap_content"android:background="@android:color/transparent"android:foreground="@drawable/selector_foreground"android:foregroundTintMode="src_in"><TextView
            android:id="@+id/id_text"android:layout_width="100dp"android:layout_height="100dp"android:text="NO.1"android:gravity="center_horizontal|center_vertical"/></FrameLayout>

drawable:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android=""android:enterFadeDuration="@android:integer/config_shortAnimTime"android:exitFadeDuration="@android:integer/config_mediumAnimTime"><item android:state_pressed="true"><shape
            android:shape="rectangle"><solid android:color="#15000000"/></shape></item><item android:drawable="@android:color/transparent"></item></selector>

当然别忘记了在代码中给 frameLayout 设置点击事件
实现效果：

　　
　　

缺陷

　　Android在所有布局的基类 View 类中 就定义了 Foreground 这个属性，但是测试发现 运行时，只有FrameLayout布局上设置该属性才会生效。观察View的代码发现这样一段。它只针对是FrameLayout的实例做获取该styleable的操作。
　　

 case R.styleable.View_foreground:if (targetSdkVersion >= VERSION_CODES.M || this instanceof FrameLayout) {setForeground(a.getDrawable(attr));}break;case R.styleable.View_foregroundGravity:if (targetSdkVersion >= VERSION_CODES.M || this instanceof FrameLayout) {setForegroundGravity(a.getInt(attr, Gravity.NO_GRAVITY));}break;

解决方案

　　模拟，FrameLayout的相关实现为TextView添加foreGround的代码功能

public class ForegroundTextView extends TextView {// UIprivate Drawable foreground;// Controller/logic fieldsprivate final Rect rectPadding = new Rect();private boolean foregroundPadding = false;private boolean foregroundBoundsChanged = false;private boolean backgroundAsForeground = false;// Constructorspublic ForegroundTextView(Context context) {super(context);}public ForegroundTextView(Context context, AttributeSet attrs) {this(context, attrs, 0);}public ForegroundTextView(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ForegroundLayout, defStyle, 0);final Drawable d = a.getDrawable(R.styleable.ForegroundLayout_foreground);foregroundPadding = a.getBoolean(R.styleable.ForegroundLayout_foregroundInsidePadding, false);backgroundAsForeground = a.getBoolean(R.styleable.ForegroundLayout_backgroundAsForeground, false);// Apply foreground padding for ninepatches automaticallyif (!foregroundPadding && getBackground() instanceof NinePatchDrawable) {final NinePatchDrawable npd = (NinePatchDrawable) getBackground();if (npd != null && npd.getPadding(rectPadding)) {foregroundPadding = true;}}final Drawable b = getBackground();if (backgroundAsForeground && b != null) {setForeground(b);} else if (d != null) {setForeground(d);}a.recycle();}/*** Supply a Drawable that is to be rendered on top of all of the child views in the layout.** @param drawable The Drawable to be drawn on top of the children.*/public void setForeground(Drawable drawable) {if (foreground != drawable) {if (foreground != null) {foreground.setCallback(null);unscheduleDrawable(foreground);}foreground = drawable;if (drawable != null) {setWillNotDraw(false);drawable.setCallback(this);if (drawable.isStateful()) {drawable.setState(getDrawableState());}} else {setWillNotDraw(true);}requestLayout();invalidate();}}/*** Returns the drawable used as the foreground of this layout. The foreground drawable,* if non-null, is always drawn on top of the children.** @return A Drawable or null if no foreground was set.*/public Drawable getForeground() {return foreground;}@Overrideprotected void drawableStateChanged() {super.drawableStateChanged();if (foreground != null && foreground.isStateful()) {foreground.setState(getDrawableState());}}@Overrideprotected boolean verifyDrawable(Drawable who) {return super.verifyDrawable(who) || (who == foreground);}@Overridepublic void jumpDrawablesToCurrentState() {super.jumpDrawablesToCurrentState();if (foreground != null) {foreground.jumpToCurrentState();}}@Override protected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);foregroundBoundsChanged = true;}@Overridepublic void draw(Canvas canvas) {super.draw(canvas);if (foreground != null) {final Drawable foreground = this.foreground;if (foregroundBoundsChanged) {foregroundBoundsChanged = false;final int w = getRight() - getLeft();final int h = getBottom() - getTop();if (foregroundPadding) {foreground.setBounds(rectPadding.left, rectPadding.top, w - rectPadding.right, h - rectPadding.bottom);} else {foreground.setBounds(0, 0, w, h);}}foreground.draw(canvas);}}@TargetApi(Build.VERSION_CODES.LOLLIPOP) @Override public boolean onTouchEvent(MotionEvent e) {if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {if (e.getActionMasked() == MotionEvent.ACTION_DOWN) {if (foreground != null) {foreground.setHotspot(e.getX(), e.getY());}}}return super.onTouchEvent(e);}
}

Andorid

Andorid-foreground 解析

---

foreground 前景色

　　foreground 也就是前景色，它与background相对应，顾名思义，它指定的drawable是在view视图的上方绘制的。

开发实例

1.实现遮罩层：

<FrameLayout
        android:id="@+id/id_frameLayout"android:layout_width="wrap_content"android:layout_height="wrap_content"android:foreground="#aaff0000"android:foregroundTintMode="src_in"><TextView
            android:id="@+id/id_text"android:layout_width="100dp"android:layout_height="100dp"android:text="NO.1"android:gravity="center_horizontal|center_vertical"/></FrameLayout>

实现效果
2.实现点击效果
　　属性能设置为drawable，我们自然就想到了也可以使用 selector drawable，在点击时套上drawable来实现类似点击效果的功能

xml代码:

    <FrameLayout
        android:id="@+id/id_frameLayout"android:layout_width="wrap_content"android:layout_height="wrap_content"android:background="@android:color/transparent"android:foreground="@drawable/selector_foreground"android:foregroundTintMode="src_in"><TextView
            android:id="@+id/id_text"android:layout_width="100dp"android:layout_height="100dp"android:text="NO.1"android:gravity="center_horizontal|center_vertical"/></FrameLayout>

drawable:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android=""android:enterFadeDuration="@android:integer/config_shortAnimTime"android:exitFadeDuration="@android:integer/config_mediumAnimTime"><item android:state_pressed="true"><shape
            android:shape="rectangle"><solid android:color="#15000000"/></shape></item><item android:drawable="@android:color/transparent"></item></selector>

当然别忘记了在代码中给 frameLayout 设置点击事件
实现效果：

　　
　　

缺陷

　　Android在所有布局的基类 View 类中 就定义了 Foreground 这个属性，但是测试发现 运行时，只有FrameLayout布局上设置该属性才会生效。观察View的代码发现这样一段。它只针对是FrameLayout的实例做获取该styleable的操作。
　　

 case R.styleable.View_foreground:if (targetSdkVersion >= VERSION_CODES.M || this instanceof FrameLayout) {setForeground(a.getDrawable(attr));}break;case R.styleable.View_foregroundGravity:if (targetSdkVersion >= VERSION_CODES.M || this instanceof FrameLayout) {setForegroundGravity(a.getInt(attr, Gravity.NO_GRAVITY));}break;

解决方案

　　模拟，FrameLayout的相关实现为TextView添加foreGround的代码功能

public class ForegroundTextView extends TextView {// UIprivate Drawable foreground;// Controller/logic fieldsprivate final Rect rectPadding = new Rect();private boolean foregroundPadding = false;private boolean foregroundBoundsChanged = false;private boolean backgroundAsForeground = false;// Constructorspublic ForegroundTextView(Context context) {super(context);}public ForegroundTextView(Context context, AttributeSet attrs) {this(context, attrs, 0);}public ForegroundTextView(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ForegroundLayout, defStyle, 0);final Drawable d = a.getDrawable(R.styleable.ForegroundLayout_foreground);foregroundPadding = a.getBoolean(R.styleable.ForegroundLayout_foregroundInsidePadding, false);backgroundAsForeground = a.getBoolean(R.styleable.ForegroundLayout_backgroundAsForeground, false);// Apply foreground padding for ninepatches automaticallyif (!foregroundPadding && getBackground() instanceof NinePatchDrawable) {final NinePatchDrawable npd = (NinePatchDrawable) getBackground();if (npd != null && npd.getPadding(rectPadding)) {foregroundPadding = true;}}final Drawable b = getBackground();if (backgroundAsForeground && b != null) {setForeground(b);} else if (d != null) {setForeground(d);}a.recycle();}/*** Supply a Drawable that is to be rendered on top of all of the child views in the layout.** @param drawable The Drawable to be drawn on top of the children.*/public void setForeground(Drawable drawable) {if (foreground != drawable) {if (foreground != null) {foreground.setCallback(null);unscheduleDrawable(foreground);}foreground = drawable;if (drawable != null) {setWillNotDraw(false);drawable.setCallback(this);if (drawable.isStateful()) {drawable.setState(getDrawableState());}} else {setWillNotDraw(true);}requestLayout();invalidate();}}/*** Returns the drawable used as the foreground of this layout. The foreground drawable,* if non-null, is always drawn on top of the children.** @return A Drawable or null if no foreground was set.*/public Drawable getForeground() {return foreground;}@Overrideprotected void drawableStateChanged() {super.drawableStateChanged();if (foreground != null && foreground.isStateful()) {foreground.setState(getDrawableState());}}@Overrideprotected boolean verifyDrawable(Drawable who) {return super.verifyDrawable(who) || (who == foreground);}@Overridepublic void jumpDrawablesToCurrentState() {super.jumpDrawablesToCurrentState();if (foreground != null) {foreground.jumpToCurrentState();}}@Override protected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);foregroundBoundsChanged = true;}@Overridepublic void draw(Canvas canvas) {super.draw(canvas);if (foreground != null) {final Drawable foreground = this.foreground;if (foregroundBoundsChanged) {foregroundBoundsChanged = false;final int w = getRight() - getLeft();final int h = getBottom() - getTop();if (foregroundPadding) {foreground.setBounds(rectPadding.left, rectPadding.top, w - rectPadding.right, h - rectPadding.bottom);} else {foreground.setBounds(0, 0, w, h);}}foreground.draw(canvas);}}@TargetApi(Build.VERSION_CODES.LOLLIPOP) @Override public boolean onTouchEvent(MotionEvent e) {if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {if (e.getActionMasked() == MotionEvent.ACTION_DOWN) {if (foreground != null) {foreground.setHotspot(e.getX(), e.getY());}}}return super.onTouchEvent(e);}
}

本文标签： Andorid