Android Custom ViewGroup Fast Sliding (4) _android

Last article Custom ViewGroup (3) Address: http://www.jb51.net/article/100618.htm

Code:

Package com.example.libingyuan.horizontallistview.ScrollViewGroup;
Import Android.content.Context;
Import Android.util.AttributeSet;
Import Android.util.DisplayMetrics;
Import android.view.MotionEvent;
Import Android.view.VelocityTracker;
Import Android.view.View;
Import android.view.ViewConfiguration;
Import Android.view.ViewGroup;
Import Android.view.WindowManager;

Import Android.widget.Scroller; /** * Custom ViewGroup * Added acceleration slide/public Class Scrollviewgroup extends ViewGroup {//scrolling compute auxiliary class private scroller Mscrol
  Ler
  The x coordinate of the finger placement is private float Mlastmotionx = 0;
  Screen width private int screenwidth;
  Finger acceleration Auxiliary class private Velocitytracker mvelocitytracker;
  The smallest DP private int mminimumvelocity moved per second;

  The largest DP private int mmaximumvelocity moved per second; /** * When creating objects using the New keyword, call * * @param context Contexts/public Scrollviewgroup {
  , null); /** * When used in XML files, call * * @param context * @param attrs properties: such as Android:layout_widTh= "Wrap_content" * * Public scrollviewgroup (context, AttributeSet attrs) {This (context, attrs, 0); /** * is invoked in an XML file and is invoked with a custom attribute (* * @param context * @param attrs properties: such as android:layout_width= "Wra P_content "* @param defstyleattr ID of the custom attribute/public Scrollviewgroup (context, AttributeSet attrs, int defst
    YLEATTR) {Super (context, attrs, defstyleattr);
  Init (context);  /** * Initialization Method * Initializes the scrolling helper class scroller and calculates the screen width * * @param context/private void Init
    {//Initialize auxiliary class Mscroller = new Scroller (context);
    Get screen width WindowManager manager = (windowmanager) context. Getsystemservice (Context.window_service);
    Displaymetrics outmetrics = new Displaymetrics ();
    Manager.getdefaultdisplay (). Getmetrics (Outmetrics);
    ScreenWidth = Outmetrics.widthpixels;
    Get the minimum and maximum moving distance final viewconfiguration configuration = viewconfiguration.get (context); Mminimumvelocity = COnfiguration.getscaledminimumflingvelocity ();
  Mmaximumvelocity = Configuration.getscaledmaximumflingvelocity (); /** * The method that needs to be overridden when rolling * is used to control scrolling/@Override public void Computescroll () {//To stop if scrolling (mscroller.compute
      Scrolloffset ()) {//scroll to the specified position Scrollto (Mscroller.getcurrx (), Mscroller.getcurry ());
    This sentence must be written, otherwise not real-time refresh postinvalidate ();  /** * Finger touchscreen event Monitor/@Override public boolean ontouchevent (Motionevent event) {//TODO auto-generated
    Method Stub int action = Event.getaction ();
    Gets the x-coordinate of the position where the finger is now in the x = Event.getx (); To determine the trigger time switch (action) {//press event case Motionevent.action_down://Initialize or take acceleration tester Initorrese
        Tvelocitytracker ();
        The tester adds the press event mvelocitytracker.addmovement (events);
        If you stop scrolling, the animation is canceled (that is, the finger presses to stop scrolling) if (!mscroller.isfinished ()) {mscroller.abortanimation ();
    //Get now X coordinate Mlastmotionx = Event.getx ();    Break Move Event Case Motionevent.action_move://Tester Add move Event if (Mvelocitytracker!= null) {mvelocity
        Tracker.addmovement (event);
        //Calculate the offset of the movement float delt = mlastmotionx-x;
        Reset Finger position Mlastmotionx = x;
        Rolling Scrollby ((int) delt, 0);
      Break
        Finger Lift Event Case MOTIONEVENT.ACTION_UP://Tester Add lift event mvelocitytracker.addmovement;
        To add the acceleration test time, here is measured within 1000 milliseconds of the acceleration mvelocitytracker.computecurrentvelocity (1000, mmaximumvelocity);
        Get x direction acceleration Float pxsec = mvelocitytracker.getxvelocity ();
        Get the last child view view LastChild = Getchildat (Getchildcount ()-1); Gets the maximum sliding distance of the slide (the coordinates of the last child's right border minus the screen width) int finalychild = (int) (LASTCHILD.GETX () + lastchild.getwidth ()-SCREENWI
        DTH); If the acceleration of x is greater than the minimum moving distance set by the system, it can be inertial sliding if (Math.Abs (pxsec) > Mminimumvelocity) mscroller.fling (GETSCROLLX (), 0, (int)-pxsec, 0, 0, finalychild, 0, 0);
        If the sliding distance is less than the leftmost (0) of the first control, the rebound to (0,0) point if (GETSCROLLX () < 0) {scrollto (0, 0);
        //If the sliding distance is greater than the maximum sliding distance, slide to the last child view if (GETSCROLLX () >= finalychild) Scrollto (finalychild, 0);
        Refresh interface invalidate ();
        Empty the tester recyclevelocitytracker ();
      Break
    Default:break;
  return true; /** * Create or reuse acceleration tester/private void Initorresetvelocitytracker () {if (Mvelocitytracker = null) {MV
    Elocitytracker = Velocitytracker.obtain ();
    else {mvelocitytracker.clear ();
      }/** * Recovery acceleration tester to prevent memory leaks/private void Recyclevelocitytracker () {if (Mvelocitytracker!= null) {
      Mvelocitytracker.recycle ();
    Mvelocitytracker = null; }} @Override protected void onmeasure (int widthmeasurespec, int heightmeasurespec) {//Reset width High This.setmeas Ureddimension (Measurewidth (Widthmeasurespec, HeightmeasuresPEC), Measureheight (Widthmeasurespec, Heightmeasurespec)); /** * Measuring width */private int measurewidth (int widthmeasurespec, int heightmeasurespec) {//width int size
    Width = Measurespec.getsize (Widthmeasurespec);
    int modewidth = Measurespec.getmode (Widthmeasurespec);
    The width of the parent control (wrap_content) int width = 0;

    int childcount = Getchildcount ();
      Re-measure the width of the child View and the maximum height for (int i = 0; i < ChildCount i++) {View children = getchildat (i);
      Measurechild (Child, Widthmeasurespec, Heightmeasurespec);
      Marginlayoutparams LP = (marginlayoutparams) child.getlayoutparams ();
      int childwidth = child.getmeasuredwidth () + Lp.leftmargin + lp.rightmargin;
    width + + childwidth; return modewidth = = measurespec.exactly?
  Sizewidth:width; /** * Measuring Height * * private int measureheight (int widthmeasurespec, int heightmeasurespec) {//height int Sizeh
    eight = Measurespec.getsize (HEIGHTMEASURESPEC); int modeheight = MeasureSPec.getmode (HEIGHTMEASURESPEC);
    The height (wrap_content) int height = 0 of the parent control;

    int childcount = Getchildcount ();
      Re-measure the width of the child View and the maximum height for (int i = 0; i < ChildCount i++) {View children = getchildat (i);
      Measurechild (Child, Widthmeasurespec, Heightmeasurespec);
      Marginlayoutparams LP = (marginlayoutparams) child.getlayoutparams ();
      int childheight = child.getmeasuredheight () + Lp.topmargin + lp.bottommargin;
    Height + = childheight;
    Height = Height/childcount; return modeheight = = measurespec.exactly?
  Sizeheight:height; /** * Give sub layout set position * * @Override protected void OnLayout (Boolean changed, int l, int t, int r, int b) {int Childleft = 0;//to the left of the space int childwidth;//view width int height = getheight ()//Screen width int childcount = Getchil
      DCount ();//number of view (int i = 0; i < ChildCount; i++) {View child = Getchildat (i); Marginlayoutparams LP = (marginlayoutparams) Child.getlayoutparaMS ();
      Childwidth = child.getmeasuredwidth () + Lp.leftmargin + lp.rightmargin;
      Child.layout (childleft, 0, Childleft + childwidth, height);
    Childleft + = Childwidth; } @Override Public Layoutparams generatelayoutparams (AttributeSet attrs) {return new Marginlayoutparams (getc
  Ontext (), attrs);
 }

}

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