请问怎么实现像酷狗音乐那样来回拖动

鼠标是慢慢拖动当鼠标放开的时候如果拖动的宽度超过模拟器宽度的一半就显示下一View
如果不到一半就会弹回去请问怎么实现
或者说用什么控件能实现

launcher源码中的WorkSpace，其实就是onScroll等方法的使用，网上搜索很多资料。

package com.renrenwei.view;import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;public class ScrollLayout extends ViewGroup { private static final String TAG = "ScrollLayout";
private Scroller mScroller;
private VelocityTracker mVelocityTracker;
private int mCurScreen;
private int mDefaultScreen = 0;
private static final int TOUCH_STATE_REST = 0;
private static final int TOUCH_STATE_SCROLLING = 1;
private static final int SNAP_VELOCITY = 600;
private int mTouchState = TOUCH_STATE_REST;
private int mTouchSlop;
private float mLastMotionX;
private float mLastMotionY; public ScrollLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0);
} public ScrollLayout(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mScroller = new Scroller(context);
mCurScreen = mDefaultScreen;
mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
} @Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
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) {
Log.e(TAG, "onMeasure");
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
final int width = MeasureSpec.getSize(widthMeasureSpec);
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
if (widthMode != MeasureSpec.EXACTLY) {
throw new IllegalStateException(
"ScrollLayout only canmCurScreen run at EXACTLY mode!");
}
final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
if (heightMode != MeasureSpec.EXACTLY) {
throw new IllegalStateException(
"ScrollLayout only can run at EXACTLY mode!");
}
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) {
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
}
} public void setToScreen(int whichScreen) {
whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
mCurScreen = whichScreen;
scrollTo(whichScreen * getWidth(), 0);
} public int getCurScreen() {
return mCurScreen;
} @Override
public void computeScroll() {
if (mScroller.computeScrollOffset()) {
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
postInvalidate();
}
} @Override
public boolean onTouchEvent(MotionEvent event) {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(event);
final int action = event.getAction();
final float x = event.getX();
final float y = event.getY();
switch (action) {
case MotionEvent.ACTION_DOWN:
Log.e(TAG, "event down!");
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
mLastMotionX = x;
break;
case MotionEvent.ACTION_MOVE:
int deltaX = (int) (mLastMotionX - x);
mLastMotionX = x;
scrollBy(deltaX, 0);
break;
case MotionEvent.ACTION_UP:
Log.e(TAG, "event : up");
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000);
int velocityX = (int) velocityTracker.getXVelocity();
Log.e(TAG, "velocityX:" + velocityX);
if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
// Fling enough to move left
Log.e(TAG, "snap left");
snapToScreen(mCurScreen - 1); } else if (velocityX < -SNAP_VELOCITY
&& mCurScreen < getChildCount() - 1) {
// Fling enough to move right
Log.e(TAG, "snap right");
snapToScreen(mCurScreen + 1);
} else {
snapToDestination();
}
// if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
//
// // Fling enough to move left
//
// Log.e(TAG, "snap left");
// if (mCurScreen > getChildCount() - 1) {
// View v1 = getChildAt(0);
// View v2 = getChildAt(1);
// View v3 = getChildAt(2);
//
// }
// snapToScreen(mCurScreen - 1);
//
// } else if (velocityX < -SNAP_VELOCITY
//
// && mCurScreen < getChildCount() - 1) {
//
// // Fling enough to move right
//
// Log.e(TAG, "snap right");
//
// snapToScreen(mCurScreen + 1);
//
// } else {
//
// snapToDestination();
//
// }
//
// if (mVelocityTracker != null) {
//
// mVelocityTracker.recycle();
//
// mVelocityTracker = null;
//
// }
// }
mTouchState = TOUCH_STATE_REST;
break;
case MotionEvent.ACTION_CANCEL:
mTouchState = TOUCH_STATE_REST;
break;
}
return true;
} @Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
// TODO Auto-generated method stub
Log.e(TAG, "onInterceptTouchEvent-slop:" + mTouchSlop + "; action = "
+ ev.getAction());
final int action = ev.getAction();
if ((action == MotionEvent.ACTION_MOVE)
&& (mTouchState != TOUCH_STATE_REST)) {
Log.e(TAG, "onInterceptTouchEvent-action:" + action);
return true;
}
final float x = ev.getX();
final float y = ev.getY();
switch (action) {
case MotionEvent.ACTION_MOVE: final int xDiff = (int) Math.abs(mLastMotionX - x);
Log.e(TAG, "onInterceptTouchEvent-move: xDiff = " + xDiff
+ "; mLastMotionX = " + mLastMotionX);
if (xDiff > mTouchSlop) { mTouchState = TOUCH_STATE_SCROLLING;
}
break;
case MotionEvent.ACTION_DOWN:
mLastMotionX = x;
mLastMotionY = y;
Log.e(TAG, "onInterceptTouchEvent-down: x = " + x + "; y = " + y);
mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
: TOUCH_STATE_SCROLLING;
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
Log.e(TAG, "onInterceptTouchEvent-up: mLastMotionX = "
+ mLastMotionX);
mTouchState = TOUCH_STATE_REST;
break;
}
return mTouchState != TOUCH_STATE_REST;
}
}<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@color/White"
    android:orientation="vertical" >    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="300dip"
        android:orientation="vertical" >
    </LinearLayout>    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_marginBottom="20dip"
        android:layout_marginLeft="15dip"
        android:layout_marginRight="15dip"
        android:background="@drawable/view_yuan_morelist" >        <com.renrenwei.view.ScrollLayout
            android:id="@+id/ScrollLayoutTest"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" >            <LinearLayout
                android:layout_width="fill_parent"
                android:layout_height="fill_parent" >                <ImageView
                    android:layout_width="fill_parent"
                    android:layout_height="fill_parent"
                    android:src="@drawable/one" />
            </LinearLayout>            <LinearLayout
                android:layout_width="fill_parent"
                android:layout_height="fill_parent" >                <ImageView
                    android:layout_width="fill_parent"
                    android:layout_height="fill_parent"
                    android:src="@drawable/two" />
            </LinearLayout>            <LinearLayout
                android:layout_width="fill_parent"
                android:layout_height="fill_parent" >                <ImageView
                    android:layout_width="fill_parent"
                    android:layout_height="fill_parent"
                    android:src="@drawable/three" />
            </LinearLayout>
        </com.renrenwei.view.ScrollLayout>
    </LinearLayout></LinearLayout>

利用viewGroup 重载computeScroller，onInterceptTouchEvent,onTouchEvent,然后可以根据你的需要选择scrollTo

调试易

请问怎么实现像酷狗音乐那样来回拖动

解决方案 »