Android实现跟随手指拖动并自动贴边的View样式(实例demo)

/** * 根据手指拖动的当前位置，自动贴边的View */public class DragView extends ImageView implements View.OnTouchListener{ private int screenWidth; private int screenHeight; private Context mContext; private int lastX, lastY; private int left ,top; private ViewGroup.MarginLayoutParams layoutParams; private int startX; private int endX; private boolean isMoved = false; private onDragViewClickListener mLister; public interface onDragViewClickListener{  void onDragViewClick(); } public void setOnDragViewClickListener(onDragViewClickListener listener){  this.mLister = listener; } public DragView(Context context) {  this(context,null); } public DragView(Context context, AttributeSet attrs) {  super(context, attrs);  mContext = context;  DisplayMetrics displayMetrics = getResources().getDisplayMetrics();  screenWidth = displayMetrics.widthPixels;  screenHeight = displayMetrics.heightPixels-getStatusBarHeight();  init(); } public void init(){  setOnTouchListener(this);  post(new Runnable() {   @Override   public void run() {    layoutParams = (ViewGroup.MarginLayoutParams)getLayoutParams();    layoutParams.topMargin = screenHeight - getHeight();    layoutParams.leftMargin = screenWidth - getWidth();    setLayoutParams(layoutParams);   }  }); } @Override public boolean onTouch(View v, MotionEvent event) {  switch (event.getAction()) {   case MotionEvent.ACTION_DOWN:    lastX = (int) event.getRawX();    lastY = (int) event.getRawY();    startX = lastX;    break;   case MotionEvent.ACTION_MOVE:    isMoved = true;    int dx = (int) event.getRawX() - lastX;    int dy = (int) event.getRawY() - lastY;    left = v.getLeft() + dx;    top = v.getTop() + dy;    int right = v.getRight() + dx;    int bottom = v.getBottom() + dy;    // 设置不能出界    if (left < 0) {     left = 0;     right = left + v.getWidth();    }    if (right > screenWidth) {     right = screenWidth;     left = right - v.getWidth();    }    if (top < 0) {     top = 0;     bottom = top + v.getHeight();    }    if (bottom > screenHeight) {     bottom = screenHeight;     top = bottom - v.getHeight();    }    v.layout(left, top, right, bottom );    lastX = (int) event.getRawX();    lastY = (int) event.getRawY();    break;   case MotionEvent.ACTION_UP:    //只有滑动改变上边距时，抬起才进行设置    if (isMoved) {     layoutParams = (ViewGroup.MarginLayoutParams)getLayoutParams();     layoutParams.topMargin = top;     setLayoutParams(layoutParams);    }    endX = (int) event.getRawX();    //滑动距离比较小，当作点击事件处理    if (Math.abs(startX - endX) < 6) {     return false;    }    if (left +v.getWidth()/2 < screenWidth/2) {     startScroll(left,screenWidth/2,true);    } else {     startScroll(left,screenWidth/2,false);    }    break;  }  return true;} //在此处理点击事件 @Override public boolean onTouchEvent(MotionEvent event) {  mLister.onDragViewClick();  return super.onTouchEvent(event); } public void startScroll(final int start, int end, final boolean isLeft){  ValueAnimator valueAnimator = ValueAnimator.ofFloat(start,end).setDuration(800);  valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {   @Override   public void onAnimationUpdate(ValueAnimator animation) {    if (isLeft) {     layoutParams.leftMargin = (int) (start*(1-animation.getAnimatedFraction()));    } else {     layoutParams.leftMargin = (int) (start + (screenWidth - start - getWidth())*(animation.getAnimatedFraction()));    }    setLayoutParams(layoutParams);   }  });  valueAnimator.start(); } /**  * 获取状态栏的高度  * @return 状态栏高度  */ public int getStatusBarHeight() {  int result = 0;  int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");  if (resourceId > 0) {   result = getResources().getDimensionPixelSize(resourceId);  }  return result; }}