android让你的TabHost滑动起来

在Android应用中，一般TabActivity和若干个Tab选项卡（TabWidget）。如果选项卡的数量超过了5个，就不适合放到一个屏幕中，这样可以让这些选项卡滑动起来。
滑动的选项卡的实现有好几种方式，在这些方式中，最简单也是我最满意的还是在原生的TabActivity上修改，将上面的选项卡改为可滑动的状态。这样既有新的滑动的效果，也保留了原有TabActivity的各项功能。
实现Tab可滑动基本的思路就是把上面的TabWidget放到一个HorizontalScrollView中，让TabWidget滑动起来。不过如果仅仅修改XML还是会产生问题，就是没有办法控制每个选项卡的宽度。所以还是需要在程序中设置每个选项卡的宽度。例如：

// 设置窗口的宽度 
DisplayMetrics dm = new DisplayMetrics(); 
getWindowManager().getDefaultDisplay().getMetrics(dm); 
int screenWidth = dm.widthPixels; 
if (count < 4) { 
    for (int i = 0; i < count; i++) { 
        // 设置每个选项卡的宽度 
        tabWidget.getChildTabViewAt(i).setMinimumWidth(screenWidth / 4); 
    } 
}

 

 

 
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent"> 
    <tabhost android:id="@android:id/tabhost" android:layout_width="fill_parent" 
        android:layout_height="fill_parent"> 
        <linearlayout android:orientation="vertical" 
            android:layout_width="fill_parent" android:layout_height="fill_parent"> 
            <horizontalscrollview android:layout_height="wrap_content" 
                android:layout_width="fill_parent" android:scrollbars="none"> 
                <tabwidget android:id="@android:id/tabs" 
                    android:layout_width="fill_parent" android:layout_height="60dp" /> 
             
            <framelayout android:id="@android:id/tabcontent" 
                android:layout_width="fill_parent" android:layout_height="wrap_content"
                android:layout_weight="1" /> 
         
     

 

效果图如下:

package com.xu81.testflip;

import java.util.Vector;

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.view.ViewGroup;
import android.widget.Scroller;

public class ScrollLayout extends ViewGroup {

        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 = 500;
        private int mTouchState = TOUCH_STATE_REST;
        private int mTouchSlop;
        private float mLastMotionX;
        private int sensitivity = 30;
        private boolean spring;
        private Vector listeners;

        public ScrollLayout(Context context, AttributeSet attrs) {
                super(context, attrs);
                // TODO Auto-generated constructor stub
                mScroller = new Scroller(context);
                mCurScreen = mDefaultScreen;
                mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
                listeners = new Vector();
        }

        public void addChangeListener(LayoutChangeListener listener) {
                listeners.add(listener);
        }

        @Override
        protected void onLayout(boolean changed, int l, int t, int r, int b) {
                // TODO Auto-generated method stub
                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) {
                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!");
                }

                // The children are given the same width and height as the scrollLayout
                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
                int lastIndex = mCurScreen;
                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
                }
                for (LayoutChangeListener listener : listeners)
                        listener.doChange(lastIndex, whichScreen);
        }

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

        public boolean isSpring() {
                return spring;
        }

        public void setSpring(boolean spring) {
                this.spring = spring;
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
                // TODO Auto-generated method stub
                if (mVelocityTracker == null)
                        mVelocityTracker = VelocityTracker.obtain();
                mVelocityTracker.addMovement(event);
                final int action = event.getAction();
                final float x = event.getX();
                switch (action) {
                case MotionEvent.ACTION_DOWN:
                        if (!mScroller.isFinished())
                                mScroller.abortAnimation();
                        mLastMotionX = x;
                        break;
                case MotionEvent.ACTION_MOVE:
                        int deltaX = (int) (mLastMotionX - x);
                        if (Math.abs(deltaX) > sensitivity) {
                                // 左滑动为正数、右为负数
                                if (spring) {
                                        scrollBy(deltaX, 0);
                                        mLastMotionX = x;
                                } else {
                                        final int childCount = getChildCount();
                                        boolean max = mCurScreen < childCount - 1;
                                        boolean min = mCurScreen > 0;
                                        boolean canMove = deltaX > 0 ? (max ? true : false)
                                                        : (min ? true : false);
                                        if (canMove) {
                                                scrollBy(deltaX, 0);
                                                mLastMotionX = x;
                                        }
                                }
                        }
                        break;
                case MotionEvent.ACTION_UP:
                        final VelocityTracker velocityTracker = mVelocityTracker;
                        velocityTracker.computeCurrentVelocity(1000);
                        int velocityX = (int) velocityTracker.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;
                case MotionEvent.ACTION_CANCEL:
                        mTouchState = TOUCH_STATE_REST;
                        break;
                }
                return true;
        }

        @Override
        public boolean onInterceptTouchEvent(MotionEvent ev) {
                // TODO Auto-generated method stub
                final int action = ev.getAction();
                if ((action == MotionEvent.ACTION_MOVE)
                                && (mTouchState != TOUCH_STATE_REST))
                        return true;
                final float x = ev.getX();
                switch (action) {
                case MotionEvent.ACTION_MOVE:
                        final int xDiff = (int) Math.abs(mLastMotionX - x);
                        if (xDiff > mTouchSlop)
                                mTouchState = TOUCH_STATE_SCROLLING;
                        break;
                case MotionEvent.ACTION_DOWN:
                        mLastMotionX = x;
                        mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
                                        : TOUCH_STATE_SCROLLING;
                        break;
                case MotionEvent.ACTION_CANCEL:
                case MotionEvent.ACTION_UP:
                        mTouchState = TOUCH_STATE_REST;
                        break;
                }
                return mTouchState != TOUCH_STATE_REST;
        }

}

 

这是模仿qq的滑动实现,和tab不是一个思路,也比较美观实用可以借鉴


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