Page slide switching (implementation of Sliding Screen by launcher)

The following example is also obtained from the Internet. I did not write it myself. I always wanted to learn it, but I didn't write it. I used to study the page Jump of launcher, launcher modification-source code tracking for switching between the left and right sliding screens to tell the truth, that code is a bit complicated, so it is not very thorough understanding. It is easier to see this example. Here we will learn:

First of all, let's take a look: although it's pretty fancy, It's all background images.

View the layout file:

<?xml version="1.0" encoding="utf-8"?>    <RelativeLayout android:layout_width="fill_parent" android:layout_height="fill_parent"    xmlns:android="http://schemas.android.com/apk/res/android">        <com.genius.scroll.MyScrollLayout      xmlns:android="http://schemas.android.com/apk/res/android"      android:id="@+id/ScrollLayout"      android:layout_width="fill_parent"      android:layout_height="fill_parent">        <FrameLayout      android:background="@drawable/guide01"      android:layout_width="fill_parent"      android:layout_height="fill_parent">  </FrameLayout>          <FrameLayout      android:background="@drawable/guide02"      android:layout_width="fill_parent"      android:layout_height="fill_parent">  </FrameLayout>            <FrameLayout       android:background="@drawable/guide03"       android:layout_width="fill_parent"      android:layout_height="fill_parent">        </FrameLayout>        <FrameLayout      android:background="@drawable/guide04"      android:layout_width="fill_parent"      android:layout_height="fill_parent">      </FrameLayout>        <FrameLayout      android:background="@drawable/guide05"      android:layout_width="fill_parent"      android:layout_height="fill_parent">      </FrameLayout>          </com.genius.scroll.MyScrollLayout>     <LinearLayout     android:orientation="horizontal"     android:id="@+id/llayout"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_marginBottom="24.0dip"     android:layout_alignParentBottom="true"     android:layout_centerHorizontal="true">            <ImageView android:clickable="true"          android:padding="15.0dip"         android:layout_gravity="center_vertical"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:src="@drawable/guide_round" />        <ImageView android:clickable="true"          android:padding="15.0dip"          android:layout_gravity="center_vertical"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:src="@drawable/guide_round" />        <ImageView android:clickable="true"          android:padding="15.0dip"          android:layout_gravity="center_vertical"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:src="@drawable/guide_round" />        <ImageView android:clickable="true"          android:padding="15.0dip"          android:layout_gravity="center_vertical"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:src="@drawable/guide_round" />        <ImageView android:clickable="true"          android:padding="15.0dip"          android:layout_gravity="center_vertical"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:src="@drawable/guide_round" />    </LinearLayout>   </RelativeLayout>

At the bottom of linearlayout, five buttons are put, and a custom control is used above: myscrolllayout. Next, let's look at this custom control: framelayout has five images in it.

Public class myscrolllayout extends viewgroup {Private Static final string tag = "scrolllayout"; private velocitytracker mvelocitytracker; // used to determine the animation gesture Private Static final int snap_velocity = 600; private scroller mscroeller; // sliding controller private int mcurscreen; private int mdefaultscreen = 0; private float mlastmotionx; private onviewchangelistener monviewchangelistener; Public myscrolllayout (context Co Ntext) {super (context); Init (context);} public myscrolllayout (context, attributeset attrs) {super (context, attrs); Init (context );} public myscrolllayout (context, attributeset attrs, int defstyle) {super (context, attrs, defstyle); Init (context);} private void Init (context) {mcurscreen = mdefaultscreen; mscroller = new scroller (context) ;}@ overrideprotected void onlayout (Boolean Cha Nged, int L, int T, int R, int B) {// todo auto-generated method stub if (changed) {int childleft = 0; final int childcount = getchildcount (); For (INT I = 0; I <childcount; I ++) {final view childdview = getchildat (I); If (childview. getvisibility ()! = View. gone) {final int childwidth = childview. getmeasuredwidth (); childview. layout (childleft, 0, childleft + childwidth, childview. getmeasuredheight (); childleft + = childwidth ;}}}@ overrideprotected void onmeasure (INT widthmeasurespec, int heightmeasurespec) {// todo auto-generated method stubsuper. onmeasure (widthmeasurespec, heightmeasurespec); Final int width = measurespec. getsize (widthmeasur Espec); Final int widthmode = measurespec. getmode (widthmeasurespec); Final int COUNT = getchildcount (); For (INT I = 0; I <count; I ++) {getchildat (I ). measure (widthmeasurespec, heightmeasurespec);} scrollto (mcurscreen * width, 0);} public void snaptodestination () {final int screenwidth = getwidth (); Final int destscreen = (getscrollx () + screenwidth/2)/screenwidth; snaptoscreen (destscreen);} Pu BLIC void snaptoscreen (INT whichscreen) {// get the valid layout page whichscreen = math. max (0, math. min (whichscreen, getchildcount ()-1); If (getscrollx ()! = (Whichscreen * getwidth () {final int Delta = whichscreen * getwidth ()-getscrollx (); mscroller. startscroll (getscrollx (), 0, Delta, 0, math. ABS (DELTA) * 2); mcurscreen = whichscreen; invalidate (); // redraw the layout if (monviewchangelistener! = NULL) {monviewchangelistener. onviewchange (mcurscreen) ;}}@ overridepublic void computescroll () {// todo auto-generated method stubif (mscroller. computescroloffset () {scrollto (mscroller. getcurrx (), mscroller. getcurry (); postinvalidate () ;}@ overridepublic Boolean ontouchevent (motionevent event) {// todo auto-generated method stub final int action = event. getaction (); Final float x = event. Getx (); Final float y = event. gety (); Switch (Action) {Case motionevent. action_down: log. I ("", "ontouchevent action_down"); If (mvelocitytracker = NULL) {mvelocitytracker = velocitytracker. obtain (); mvelocitytracker. addmovement (event);} If (! Mscroller. isfinished () {mscroller. abortanimation ();} mlastmotionx = x; break; Case motionevent. action_move: int deltax = (INT) (mlastmotionx-x); If (iscanmove (deltax) {If (mvelocitytracker! = NULL) {mvelocitytracker. addmovement (event);} mlastmotionx = x; scrollby (deltax, 0);} break; Case motionevent. action_up: int velocityx = 0; If (mvelocitytracker! = NULL) {mvelocitytracker. addmovement (event); mvelocitytracker. computecurrentvelocity (1000); velocityx = (INT) mvelocitytracker. getxvelocity ();} If (velocityx> snap_velocity & mcurscreen> 0) {log. E (TAG, "snap left"); snaptoscreen (mcurscreen-1);} else if (velocityx <-snap_velocity & mcurscreen <getchildcount ()-1) {log. E (TAG, "snap right"); snaptoscreen (mcurscreen + 1);} else {snaptop Estination ();} If (mvelocitytracker! = NULL) {mvelocitytracker. recycle (); mvelocitytracker = NULL;} break;} return true;} private Boolean iscanmove (INT deltax) {If (getscrollx () <= 0 & deltax <0) {return false;} If (getscrollx () >=( getchildcount ()-1) * getwidth () & deltax> 0) {return false;} return true ;} public void setonviewchangelistener (onviewchangelistener listener) {monviewchangelistener = listener ;}}

First of all, he inherits the viewgroup class. Here he mainly overrides onmeasure (), ontouchevent (), and other methods. Here he uses a custom interface private onviewchangelistener monviewchangelistener. Let's take a look at its definition:

public interface OnViewChangeListener {public void OnViewChange(int view);}

This interface defines a callback method: the specific implementation of onviewchange () is in the main activity:

public class SwitchViewDemoActivity extends Activity implements OnViewChangeListener, OnClickListener{    /** Called when the activity is first created. */private MyScrollLayout mScrollLayout;private ImageView[] mImageViews;private int mViewCount;private int mCurSel;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                init();    }        private void init()    {    mScrollLayout = (MyScrollLayout) findViewById(R.id.ScrollLayout);     LinearLayout linearLayout = (LinearLayout) findViewById(R.id.llayout);       mViewCount = mScrollLayout.getChildCount();    mImageViews = new ImageView[mViewCount];       for(int i = 0; i < mViewCount; i++)    {    mImageViews[i] = (ImageView) linearLayout.getChildAt(i);    mImageViews[i].setEnabled(true);    mImageViews[i].setOnClickListener(this);    mImageViews[i].setTag(i);    }        mCurSel = 0;    mImageViews[mCurSel].setEnabled(false);        mScrollLayout.SetOnViewChangeListener(this);    }    private void setCurPoint(int index)    {    if (index < 0 || index > mViewCount - 1 || mCurSel == index)    {    return ;    }        mImageViews[mCurSel].setEnabled(true);    mImageViews[index].setEnabled(false);        mCurSel = index;    }    @Overridepublic void OnViewChange(int view) {// TODO Auto-generated method stubsetCurPoint(view);}@Overridepublic void onClick(View v) {// TODO Auto-generated method stubint pos = (Integer)(v.getTag());setCurPoint(pos);mScrollLayout.snapToScreen(pos);}}

This onviewchange () method mainly calls the setcurpoint () method to complete the page Jump. The snaptoscreen () method in myscrolllayout is a typical callback method:

public void snapToScreen(int whichScreen) {            // get the valid layout page            whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1));            if (getScrollX() != (whichScreen*getWidth())) {                                final int delta = whichScreen*getWidth()-getScrollX();                      mScroller.startScroll(getScrollX(), 0,                         delta, 0, Math.abs(delta)*2);                        mCurScreen = whichScreen;                invalidate();       // Redraw the layout                            if (mOnViewChangeListener != null)            {            mOnViewChangeListener.OnViewChange(mCurScreen);            }        }        } 

mOnViewChangeListener.OnViewChange(mCurScreen);

This code is a typical callback.

In the ontouchevent () method of myscrolllayout, it is a response to the touch screen event:

final int action = event.getAction();            final float x = event.getX();            final float y = event.getY();                        switch (action) {            case MotionEvent.ACTION_DOWN:                   Log.i("", "onTouchEvent  ACTION_DOWN");                  if (mVelocityTracker == null) {                mVelocityTracker = VelocityTracker.obtain();                mVelocityTracker.addMovement(event);     }                     if (!mScroller.isFinished()){                    mScroller.abortAnimation();                }                            mLastMotionX = x;                       break;                            case MotionEvent.ACTION_MOVE:             int deltaX = (int)(mLastMotionX - x);                      if (IsCanMove(deltaX)){         if (mVelocityTracker != null){              mVelocityTracker.addMovement(event);            }                 mLastMotionX = x;                   scrollBy(deltaX, 0);           }                  break;                            case MotionEvent.ACTION_UP:                       int velocityX = 0;            if (mVelocityTracker != null){            mVelocityTracker.addMovement(event);             mVelocityTracker.computeCurrentVelocity(1000);              velocityX = (int) mVelocityTracker.getXVelocity();            }                                           if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {                             Log.e(TAG, "snap left");                    snapToScreen(mCurScreen - 1);                   } else if (velocityX < -SNAP_VELOCITY                           && mCurScreen < getChildCount() - 1) {                           Log.e(TAG, "snap right");                    snapToScreen(mCurScreen + 1);                   } else {                       snapToDestination();                   }                                          if (mVelocityTracker != null) {                       mVelocityTracker.recycle();                       mVelocityTracker = null;                   }                   break;              }           

Make different responses by judging the moving distance and the moving direction.

Other codes are easy to understand. You are welcome to discuss any issues. The following is the code:

Http://download.csdn.net/detail/aomandeshangxiao/4017928