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package com.examples.customtouch.widget; /*from w w w. j a v a 2 s . c o m*/ import android.content.Context; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.widget.FrameLayout; import android.widget.OverScroller; public class TwoDimensionScrollView extends FrameLayout { //Fling components private OverScroller mScroller; private VelocityTracker mVelocityTracker; /* Positions of the last motion event */ private float mLastTouchX, mLastTouchY; /* Drag threshold */ private int mTouchSlop; /* Fling Velocity */ private int mMaximumVelocity, mMinimumVelocity; /* Drag Lock */ private boolean mDragging = false; public TwoDimensionScrollView(Context context) { super(context); init(context); } public TwoDimensionScrollView(Context context, AttributeSet attrs) { super(context, attrs); init(context); } public TwoDimensionScrollView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(context); } private void init(Context context) { mScroller = new OverScroller(context); mVelocityTracker = VelocityTracker.obtain(); //Get system constants for touch thresholds mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop(); mMaximumVelocity = ViewConfiguration.get(context).getScaledMaximumFlingVelocity(); mMinimumVelocity = ViewConfiguration.get(context).getScaledMinimumFlingVelocity(); } /* * Override the measureChild... implementations to guarantee that the child view * gets measured to be as large as it wants to be. The default implementation will * force some children to be only as large as this view. */ @Override protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { int childWidthMeasureSpec; int childHeightMeasureSpec; childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } @Override protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) { final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { // This is called at drawing time by ViewGroup. We use // this method to keep the fling animation going through // to completion. int oldX = getScrollX(); int oldY = getScrollY(); int x = mScroller.getCurrX(); int y = mScroller.getCurrY(); if (getChildCount() > 0) { View child = getChildAt(0); x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth()); y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight()); if (x != oldX || y != oldY) { scrollTo(x, y); } } // Keep on drawing until the animation has finished. postInvalidate(); } } //Override scrollTo to do bounds checks on any scrolling request @Override public void scrollTo(int x, int y) { // we rely on the fact the View.scrollBy calls scrollTo. if (getChildCount() > 0) { View child = getChildAt(0); x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth()); y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight()); if (x != getScrollX() || y != getScrollY()) { super.scrollTo(x, y); } } } /* * Utility method to initialize the Scroller and start redrawing */ public void fling(int velocityX, int velocityY) { if (getChildCount() > 0) { int height = getHeight() - getPaddingBottom() - getPaddingTop(); int width = getWidth() - getPaddingLeft() - getPaddingRight(); int bottom = getChildAt(0).getHeight(); int right = getChildAt(0).getWidth(); mScroller.fling(getScrollX(), getScrollY(), velocityX, velocityY, 0, Math.max(0, right - width), 0, Math.max(0, bottom - height)); invalidate(); } } /* * Utility method to assist in doing bounds checking */ private int clamp(int n, int my, int child) { if (my >= child || n < 0) { /* my >= child is this case: * |--------------- me ---------------| * |------ child ------| * or * |--------------- me ---------------| * |------ child ------| * or * |--------------- me ---------------| * |------ child ------| * * n < 0 is this case: * |------ me ------| * |-------- child --------| * |-- mScrollX --| */ return 0; } if ((my+n) > child) { /* this case: * |------ me ------| * |------ child ------| * |-- mScrollX --| */ return child-my; } return n; } /* * Monitor touch events passed down to the children and * intercept as soon as it is determined we are dragging. This * allows child views to still receive touch events if they are * interactive (i.e. Buttons) */ @Override public boolean onInterceptTouchEvent(MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: //Stop any flinging in progress if (!mScroller.isFinished()) { mScroller.abortAnimation(); } //Reset the velocity tracker mVelocityTracker.clear(); mVelocityTracker.addMovement(event); //Save the initial touch point mLastTouchX = event.getX(); mLastTouchY = event.getY(); break; case MotionEvent.ACTION_MOVE: final float x = event.getX(); final float y = event.getY(); final int yDiff = (int) Math.abs(y - mLastTouchY); final int xDiff = (int) Math.abs(x - mLastTouchX); //Verify that either difference is enough to be a drag if (yDiff > mTouchSlop || xDiff > mTouchSlop) { mDragging = true; mVelocityTracker.addMovement(event); //Start capturing events ourselves return true; } break; case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: mDragging = false; mVelocityTracker.clear(); break; } return super.onInterceptTouchEvent(event); } /* * Feed all touch events we receive to the detector for * processing. */ @Override public boolean onTouchEvent(MotionEvent event) { mVelocityTracker.addMovement(event); switch (event.getAction()) { case MotionEvent.ACTION_DOWN: // We've already stored the initial point, // but if we got here a child view didn't capture // the event, so we need to. return true; case MotionEvent.ACTION_MOVE: final float x = event.getX(); final float y = event.getY(); float deltaY = mLastTouchY - y; float deltaX = mLastTouchX - x; //Check for slop on direct events if (!mDragging && (Math.abs(deltaY) > mTouchSlop || Math.abs(deltaX) > mTouchSlop) ) { mDragging = true; } if (mDragging) { //Scroll the view scrollBy((int) deltaX, (int) deltaY); //Update the last touch event mLastTouchX = x; mLastTouchY = y; } break; case MotionEvent.ACTION_CANCEL: mDragging = false; //Stop any flinging in progress if (!mScroller.isFinished()) { mScroller.abortAnimation(); } break; case MotionEvent.ACTION_UP: mDragging = false; // Compute the current velocity and start a fling if it is above // the minimum threshold. mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); int velocityX = (int)mVelocityTracker.getXVelocity(); int velocityY = (int)mVelocityTracker.getYVelocity(); if (Math.abs(velocityX) > mMinimumVelocity || Math.abs(velocityY) > mMinimumVelocity) { fling(-velocityX, -velocityY); } break; } return super.onTouchEvent(event); } }