Android-Custom-Components

 <tbody>
 <tr>
 <td rowspan="2">Creation</td>
 <td>Constructors</td>
 <td>一种形式的构造方法将会在由代码创建的View和由布局文件填充的View来调用,第二种形式的构造方法应该解析和应用那些定义在布局文件的属性.
 </td>
 </tr>
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onFinishInflate()">onFinishInflate()</a></code></code></td>
 <td>当一个view和它所有的子元素从布局文件中被填充之后调用.</td>
 </tr>
 
 <tr>
 <td rowspan="3">Layout</td>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onMeasure(int, int)">onMeasure(int, int)</a></code></code></td>
 <td>用来决定view和他所以子元素的尺寸要求.
 </td>
 </tr>
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onLayout(boolean, int, int, int, int)">onLayout(boolean, int, int, int, int)</a></code></code></td>
 <td>当这个view和它的子元素需要被指定一个大小和位置的时候调用.
 </td>
 </tr>
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onSizeChanged(int, int, int, int)">onSizeChanged(int, int, int, int)</a></code></code></td>
 <td>当这个view的大小发生变化的时候调用.
 </td>
 </tr>
 
 <tr>
 <td>Drawing</td>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onDraw(android.graphics.Canvas)">onDraw(Canvas)</a></code></code></td>
 <td>当这个view需要渲染它的内容的时候调用.
 </td>
 </tr>
 <tr>
 <td rowspan="4">Event processing</td>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onKeyDown(int, android.view.KeyEvent)">onKeyDown(int, KeyEvent)</a></code></code></td>
 <td>当发送新的按键事件时调用.
 </td>
 </tr>
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onKeyUp(int, android.view.KeyEvent)">onKeyUp(int, KeyEvent)</a></code></code></td>
 <td>当按键按起的事件发生时调用.
 </td>
 </tr> 
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onTrackballEvent(android.view.MotionEvent)">onTrackballEvent(MotionEvent)</a></code></code></td>
 <td>当轨迹球移动事件发生时调用.
 </td>
 </tr> 
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onTouchEvent(android.view.MotionEvent)">onTouchEvent(MotionEvent)</a></code></code></td>
 <td>当触摸屏幕移动事件发生时调用.
 </td>
 </tr> 
 
 <tr>
 <td rowspan="2">Focus</td>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onFocusChanged(boolean, int, android.graphics.Rect)">onFocusChanged(boolean, int, Rect)</a></code></code></td>
 <td>当view获得或失去焦点时调用.
 </td>
 </tr>
 
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onWindowFocusChanged(boolean)">onWindowFocusChanged(boolean)</a></code></code></td>
 <td>当包含view的窗口获得或者失去焦点时调用.
 </td>
 </tr>
 
 <tr>
 <td rowspan="3">Attaching</td>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onAttachedToWindow()">onAttachedToWindow()</a></code></code></td>
 <td>当view添加到一个窗口时调用.
 </td>
 </tr>
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onDetachedFromWindow()">onDetachedFromWindow()</a></code></code></td>
 <td>当view从窗口分离的时候调用.
 </td>
 </tr> 
 <tr>
 <td><code><code><a href="http://www.android-doc.com/reference/android/view/View.html#onWindowVisibilityChanged(int)">onWindowVisibilityChanged(int)</a></code></code></td>
 <td>当包含view的窗口可见性发生变化时调用.
 </td>
 </tr>
 
 <tr>
 <td></td>
 <td><code><code><a>ViewConfiguration.get(context).getScaledTouchSlop()</a></code></code></td>
 <td>获取当前手机屏幕最小滑动距离,在frameworks/base/core/res/res/values/config.xml文件中.
 </td>
 </tr>
 
 </tbody>

- GestureDetector
```java
//解决长按屏幕后无法拖动的现象
gestureDetector.setIsLongpressEnabled(false);
public boolean onTouchEvent(MotionEvent event) {
 LogUtil.show(TAG, "onTouchEvent()", Log.INFO);
 return gestureDetector.onTouchEvent(event);
}
OnDoubleTapListener
OnGestureListener

//有过渡效果的滑动
Scroller scroller = new Scroller(context);
private void smoothScrollTo(int desX, int desY) {
 int scrollX = getScrollX();
 int delta = desX - scrollX;
 scroller.startScroll(scrollX, 0, desX, desY, 1000);//没有进行滑动操作
 invalidate();//View重绘
}
@Override
public void computeScroll() {
 super.computeScroll();
 if (scroller.computeScrollOffset()) {
 scrollTo(scroller.getCurrX(), scroller.getCurrY());
 invalidate();
 }
}
View
/**
 * Called by a parent to request that a child update its values for mScrollX
 * and mScrollY if necessary. This will typically be done if the child is
 * animating a scroll using a {@link android.widget.Scroller Scroller}
 * object.
 */
public void computeScroll() {
}
Scoller
/**
 * Call this when you want to know the new location. If it returns true,
 * the animation is not yet finished.
 */ 
public boolean computeScrollOffset() {
 if (mFinished) {
 return false;
 }
 int timePassed = (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
 if (timePassed < mDuration) {
 switch (mMode) {
 case SCROLL_MODE:
 //滑动的时间,计算出滑动的距离,根据起始位置,计算出当前的位置
 final float x = mInterpolator.getInterpolation(timePassed * mDurationReciprocal);
 mCurrX = mStartX + Math.round(x * mDeltaX);
 mCurrY = mStartY + Math.round(x * mDeltaY);
 break;
 case FLING_MODE:
 final float t = (float) timePassed / mDuration;
 final int index = (int) (NB_SAMPLES * t);
 float distanceCoef = 1.f;
 float velocityCoef = 0.f;
 if (index < NB_SAMPLES) {
 final float t_inf = (float) index / NB_SAMPLES;
 final float t_sup = (float) (index + 1) / NB_SAMPLES;
 final float d_inf = SPLINE_POSITION[index];
 final float d_sup = SPLINE_POSITION[index + 1];
 velocityCoef = (d_sup - d_inf) / (t_sup - t_inf);
 distanceCoef = d_inf + (t - t_inf) * velocityCoef;
 }
 mCurrVelocity = velocityCoef * mDistance / mDuration * 1000.0f;
 
 mCurrX = mStartX + Math.round(distanceCoef * (mFinalX - mStartX));
 // Pin to mMinX <= mCurrX <= mMaxX
 mCurrX = Math.min(mCurrX, mMaxX);
 mCurrX = Math.max(mCurrX, mMinX);
 
 mCurrY = mStartY + Math.round(distanceCoef * (mFinalY - mStartY));
 // Pin to mMinY <= mCurrY <= mMaxY
 mCurrY = Math.min(mCurrY, mMaxY);
 mCurrY = Math.max(mCurrY, mMinY);
 if (mCurrX == mFinalX && mCurrY == mFinalY) {
 mFinished = true;
 }
 break;
 }
 }
 else {
 mCurrX = mFinalX;
 mCurrY = mFinalY;
 mFinished = true;
 }
 return true;
}
Note:Scroller并不能实现View的滑动,需要配合View的computeScroll,通过滑动的时间,得到滑动的位置,通过scrollTo完成滑动,View的每次重绘都会调用computeScrollOffset
if (scroller.computeScrollOffset()) {
 scrollTo(scroller.getCurrX(), scroller.getCurrY());
 invalidate();
}
如果没有完成滑动,继续进行滑动

 /**
 * Pass the touch screen motion event down to the target view, or this
 * view if it is the target.
 *
 * @param event The motion event to be dispatched.
 * @return True if the event was handled by the view, false otherwise.
 */
 public boolean dispatchTouchEvent(MotionEvent event) {
 ...
 }
 ViewGroup
 public boolean onInterceptTouchEvent(MotionEvent ev) {
 return false;
 }
 public boolean onTouchEvent(MotionEvent event){
 ...
 if(onClickListener!=null){
 onClickListener.onClick();
 }
 }
 
 public void dispatchTouchEvent(MotionEvent ev){
 boolean consume=false;
 if(onInterceptTouchEvent(ev)){
 consume=onTouchEvent(ev);
 }else{
 consume=child.dispatchTouchEvent(ev);
 }
 reture consume;
 }
 
 //View的事件处理
 if(onTouchListener!=null){
 if(!onTouchListener.onTouch()){
 onTouchEvent();
 }
 }
Note:点击事件:Activity->Window->View , if(!view.onTouchEvent)->if(!parent.onTouchEvent)->...->Acrivity.onTouchEvent;
1.一个事件序列,down->move...->up;
2.一个事件序列只能被一个View拦截消耗,但可以通过其他手段将事件传递给其他View,在onTouchEvent()强行传递给其他view
3.View没有这个onInterceptTouchEvent(),直接调用onTouchEvent(),默认返回true,除非它是不可点击.
4.View的enable不影响onTouchEvent默认返回值,只要clickable||longClickable=true -> onTouchEvent()=true;
5.事件传递由外向内,事件先传递给父元素,再由其传递给子元素,requestDisallowInterceptTouchEvent可以干预父元素的事件分发但是ActionDown事件除外.
 
 interface ViewParent
 /**
 * Called when a child does not want this parent and its ancestors to
 * intercept touch events with
 * {@link ViewGroup#onInterceptTouchEvent(MotionEvent)}.
 *
 * <p>This parent should pass this call onto its parents. This parent must obey
 * this request for the duration of the touch (that is, only clear the flag
 * after this parent has received an up or a cancel.</p>
 * 
 * @param disallowIntercept True if the child does not want the parent to
 * intercept touch events.
 */
 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept);

Activity#dispatchTouchEvent()
/**
 * Called to process touch screen events. You can override this to
 * intercept all touch screen events before they are dispatched to the
 * window. Be sure to call this implementation for touch screen events
 * that should be handled normally.
 *
 * @param ev The touch screen event.
 *
 * @return boolean Return true if this event was consumed.
 */
public boolean dispatchTouchEvent(MotionEvent ev) {
 if (ev.getAction() == MotionEvent.ACTION_DOWN) {
 onUserInteraction();
 }
 if (getWindow().superDispatchTouchEvent(ev)) {
 return true;//事件处理结束
 }
 return onTouchEvent(ev);//当所有子元素没有做事件处理的时候调用onTouchEvent(ev);
}
PhoneWindow#superDispatchTouchEvent()
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
 return mDecor.superDispatchTouchEvent(event);
}
`private final class DecorView extends FrameLayout implements RootViewSurfaceTaker`
DecorView#superDispatchTouchEvent()
public boolean superDispatchTouchEvent(MotionEvent event) {
 return super.dispatchTouchEvent(event);
}
((ViewGroup)getWindow().getDecorView().findViewById(android.R.id.content)).getChildAt(0)获取Activity设置的View,由于DecorView extends FrameLayout(ViewGroup),事件传递给
ViewGroup#dispatchTouchEvent()
@Override
public boolean dispatchTouchEvent(MotionEvent ev){
 // Handle an initial down.
 if (actionMasked == MotionEvent.ACTION_DOWN) {
 // Throw away all previous state when starting a new touch gesture.
 // The framework may have dropped the up or cancel event for the previous gesture
 // due to an app switch, ANR, or some other state change.
 cancelAndClearTouchTargets(ev);
 resetTouchState();
 }
 // Check for interception.
 final boolean intercepted;
 if (actionMasked == MotionEvent.ACTION_DOWN
 || mFirstTouchTarget != null) {
 final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
 if (!disallowIntercept) {
 intercepted = onInterceptTouchEvent(ev);
 ev.setAction(action); // restore action in case it was changed
 } else {
 intercepted = false;
 }
 } else {
 // There are no touch targets and this action is not an initial down
 // so this view group continues to intercept touches.
 intercepted = true;
 }
}
顶级View也叫根View,顶级View一般来说都是ViewGroup.FLAG_DISALLOW_INTERCEPT 可以通过这个标志位处理滑动冲突的问题
当ViewGroup不拦截事件,事件会向下传递给子view