高仿launcher和墨跡左右拖動效果 – Android移動開發技術文章_手機開發 Android移動開發教學課程

半個月前就有這樣的想法，做出一個模仿launcher的效果。自己也曾從網上搜過很多資料，也思考過怎麼實現，最終還是參考瞭別人的資料實現瞭此效果，也解決瞭我這半個多月的冥思苦想，再次感謝，今天把代碼貼出來供大傢學習，因為這方面做得比較好的資料缺失比較少（因為本人搜瞭很多資料都不能達到效果），如果大傢覺得還不錯，請頂起。

首先自定義一個 ViewGroup：

[html] public class MyScrollLayout extends ViewGroup{

    private VelocityTracker mVelocityTracker;           // 用於判斷甩動手勢
    private static final int SNAP_VELOCITY = 600;
    private Scroller mScroller;                        // 滑動控制器
    private int mCurScreen;
    private int mDefaultScreen = 0;
    private float mLastMotionX;
//   private int mTouchSlop;

   private OnViewChangeListener mOnViewChangeListener;

    public MyScrollLayout(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        init(context);
    }
    public MyScrollLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        init(context);
    }

    public MyScrollLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        // TODO Auto-generated constructor stub
        init(context);
    }

    private void init(Context context)
    {
        mCurScreen = mDefaultScreen;
     //   mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
        mScroller = new Scroller(context);

    }

    @Override
    protected void onLayout(boolean changed, 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 childView = getChildAt(i);
                    if (childView.getVisibility() != View.GONE) {
                        final int childWidth = childView.getMeasuredWidth();
                        childView.layout(childLeft, 0,
                                childLeft+childWidth, childView.getMeasuredHeight());
                        childLeft += childWidth;
                    }
                }
            }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // TODO Auto-generated method stub
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        final int width = MeasureSpec.getSize(widthMeasureSpec);
        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);
     }

     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);
                }
            }
        }

    @Override
    public void computeScroll() {
        // TODO Auto-generated method stub
        if (mScroller.computeScrollOffset()) {
            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            postInvalidate();
        }
    }

    @Override
    public 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) {
                    // Fling enough to move left
                    snapToScreen(mCurScreen – 1);
                } else if (velocityX < -SNAP_VELOCITY
                        && mCurScreen < getChildCount() – 1) {
                    // Fling enough to move right
                    snapToScreen(mCurScreen + 1);
                } else {
                    snapToDestination();
                }

                if (mVelocityTracker != null) {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
          //      mTouchState = TOUCH_STATE_REST;
                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;
    }
}
public class MyScrollLayout extends ViewGroup{

    private VelocityTracker mVelocityTracker;    // 用於判斷甩動手勢
    private static final int SNAP_VELOCITY = 600;
    private Scroller mScroller;      // 滑動控制器
    private int mCurScreen;
private int mDefaultScreen = 0;
    private float mLastMotionX;
//   private int mTouchSlop;

   private OnViewChangeListener mOnViewChangeListener;

public MyScrollLayout(Context context) {
  super(context);
  // TODO Auto-generated constructor stub
  init(context);
}
public MyScrollLayout(Context context, AttributeSet attrs) {
  super(context, attrs);
  // TODO Auto-generated constructor stub
  init(context);
}

public MyScrollLayout(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  // TODO Auto-generated constructor stub
  init(context);
}

private void init(Context context)
{
  mCurScreen = mDefaultScreen;
//   mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
     mScroller = new Scroller(context);

}

@Override
protected void onLayout(boolean changed, 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 childView = getChildAt(i);
                 if (childView.getVisibility() != View.GONE) {
                     final int childWidth = childView.getMeasuredWidth();
                     childView.layout(childLeft, 0,
                             childLeft+childWidth, childView.getMeasuredHeight());
                     childLeft += childWidth;
                 }
             }
         }
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  // TODO Auto-generated method stub
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  final int width = MeasureSpec.getSize(widthMeasureSpec);
     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);
}

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);
             }
         }
     }

@Override
public void computeScroll() {
  // TODO Auto-generated method stub
  if (mScroller.computeScrollOffset()) {
            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            postInvalidate();
        }
}

@Override
public 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) {
                 // Fling enough to move left
                 snapToScreen(mCurScreen – 1);
             } else if (velocityX < -SNAP_VELOCITY
                     && mCurScreen < getChildCount() – 1) {
                 // Fling enough to move right
                 snapToScreen(mCurScreen + 1);
             } else {
                 snapToDestination();
             }

             if (mVelocityTracker != null) {
                 mVelocityTracker.recycle();
                 mVelocityTracker = null;
             }
       //      mTouchState = TOUCH_STATE_REST;
             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;
}
}

[html] 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);
        //動態添加一個layout控件
        LinearLayout layout=new LinearLayout(this);
        layout.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT));
        layout.setBackgroundResource(R.drawable.guide01);
        mScrollLayout.addView(layout);
        //動態添加一個imageView控件
        ImageView imageView=new ImageView(this);
        imageView.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
        imageView.setPadding(15, 15, 15, 15);
        imageView.setImageResource(R.drawable.guide_round);
        linearLayout.addView(imageView);

        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;
    }

    @Override
    public void OnViewChange(int view) {
        // TODO Auto-generated method stub
        setCurPoint(view);
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        int pos = (Integer)(v.getTag());
        setCurPoint(pos);
        mScrollLayout.snapToScreen(pos);
    }
}
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);
    //動態添加一個layout控件
    LinearLayout layout=new LinearLayout(this);
    layout.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT));
    layout.setBackgroundResource(R.drawable.guide01);
    mScrollLayout.addView(layout);
    //動態添加一個imageView控件
    ImageView imageView=new ImageView(this);
    imageView.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
    imageView.setPadding(15, 15, 15, 15);
    imageView.setImageResource(R.drawable.guide_round);
    linearLayout.addView(imageView);

    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;
    }

    @Override
public void OnViewChange(int view) {
  // TODO Auto-generated method stub
  setCurPoint(view);
}

@Override
public void onClick(View v) {
  // TODO Auto-generated method stub
  int pos = (Integer)(v.getTag());
  setCurPoint(pos);
  mScrollLayout.snapToScreen(pos);
}
}
最後是佈局文件：

[html] <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <cn.com.karl.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" >

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="@drawable/guide01" >
        </LinearLayout>

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="@drawable/guide02" >
        </LinearLayout>

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="@drawable/guide03" >
        </LinearLayout>

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="@drawable/guide04" >
        </LinearLayout>

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:background="@drawable/guide05" >
        </LinearLayout>
    </cn.com.karl.scroll.MyScrollLayout>

    <LinearLayout
        android:id="@+id/llayout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="24.0dip"
        android:orientation="horizontal" >

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:clickable="true"
            android:padding="15.0dip"
            android:src="@drawable/guide_round" />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:clickable="true"
            android:padding="15.0dip"
            android:src="@drawable/guide_round" />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:clickable="true"
            android:padding="15.0dip"
            android:src="@drawable/guide_round" />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:clickable="true"
            android:padding="15.0dip"
            android:src="@drawable/guide_round" />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:clickable="true"
            android:padding="15.0dip"
            android:src="@drawable/guide_round" />
    </LinearLayout>

</RelativeLayout>
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <cn.com.karl.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" >