Android中的Banner效果

第一步：
package com.example.example;import android.content.Context;import android.os.Handler;import android.os.Message;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.view.ViewGroup;import android.view.animation.DecelerateInterpolator;import android.widget.Scroller;public class BannerLayout extends ViewGroup {    private Scroller scroller;    private float mLastMotionX;    // private int mTouchSlop;    private OnItemClickListener onItemClickListener;    private int currentScreenIndex = 0;    private boolean moving = false;    private boolean autoScroll = false;    private int scrollTime = 4 * 1000;    private int currentWhat = 0;    private Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {            if (autoScroll && currentWhat == msg.what) {                currentScreenIndex = (currentScreenIndex + 1) % getChildCount();                scrollToScreen(currentScreenIndex);                Log.i("TAG", "handleMessage scrollToScreen:"                        + currentScreenIndex);                if (autoScroll)                    handler.sendEmptyMessageDelayed(currentWhat, scrollTime);            }        }    };    public BannerLayout(Context context) {        super(context);        initView(context);        // TODO Auto-generated constructor stub    }    public BannerLayout(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        // TODO Auto-generated constructor stub        initView(context);    }    public BannerLayout(Context context, AttributeSet attrs) {        super(context, attrs);        initView(context);        // TODO Auto-generated constructor stub    }    private void initView(final Context context) {        this.scroller = new Scroller(context, new DecelerateInterpolator(4));// OvershootInterpolator(1.1f)        // handler.sendEmptyMessageDelayed(currentWhat, scrollTime);        // final ViewConfiguration configuration = ViewConfiguration        // .get(getContext());        // mTouchSlop = configuration.getScaledTouchSlop();    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        // super.onMeasure(widthMeasureSpec, heightMeasureSpec);        int maxHeight = -1;        final int count = getChildCount();        for (int i = 0; i < count; i++) {            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);            maxHeight = Math.max(maxHeight, getChildAt(i).getMeasuredHeight());        }        maxHeight = Math.min(maxHeight, MeasureSpec.getSize(heightMeasureSpec));        Log.e("TAG", "onMeasure Height:" + maxHeight);        setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec), maxHeight);    }    @Override    protected void onLayout(boolean changed, int left, int top, int right,            int bottom) {        final int count = getChildCount();        int cLeft = 0;        for (int i = 0; i < count; i++) {            View child = getChildAt(i);            if (child.getVisibility() == View.GONE)                continue;            // child.setVisibility(View.VISIBLE);            final int childWidth = child.getMeasuredWidth();            child.layout(cLeft, 0, cLeft + childWidth,                    child.getMeasuredHeight());            cLeft += childWidth;        }    }    @Override    public void computeScroll() {        if (scroller.computeScrollOffset()) {            scrollTo(scroller.getCurrX(), 0);            postInvalidate();        }    }    @Override    public boolean onTouchEvent(MotionEvent ev) {        if (getChildCount() == 0)            return false;        final int action = ev.getAction();        final float x = ev.getX();        switch (action) {        case MotionEvent.ACTION_DOWN:            autoScroll = false;            currentWhat++;            mLastMotionX = x;            if (!scroller.isFinished()) {                scroller.abortAnimation();            }            moving = false;            // Log.i("TAG","ACTION_DOWN");            return true;        case MotionEvent.ACTION_MOVE:            final int deltaX = (int) (mLastMotionX - x);            boolean xMoved = Math.abs(deltaX) > 4;            if (!moving && !xMoved)                break;            mLastMotionX = x;            if ((0 == currentScreenIndex && deltaX < 0)                    || (getChildCount() - 1 == currentScreenIndex && deltaX > 0))                scrollBy(deltaX / 4, 0);            else                scrollBy(deltaX, 0);            moving = true;            {                final int screenWidth = getWidth();                currentScreenIndex = (getScrollX() + (screenWidth / 2))                        / screenWidth;            }            return true;        case MotionEvent.ACTION_UP:            snapToDestination();            if (!autoScroll) {                startScroll();            }            if (!moving && null != onItemClickListener) {                final int screenWidth = getWidth();                int index = (int) ((getScrollX() + x) / screenWidth);                onItemClickListener.onClick(index, getChildAt(index));            }            break;        case MotionEvent.ACTION_CANCEL:            snapToDestination();            if (!autoScroll) {                startScroll();            }        }        return false;    }    private void scrollToScreen(int whichScreen) {        // if (!scroller.isFinished())        // return;        // Log.e("TAG","scrollToScreen:"+whichScreen);        if (whichScreen >= getChildCount())            whichScreen = getChildCount() - 1;        int delta = 0;        delta = whichScreen * getWidth() - getScrollX();        // scroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta) * 2);        scroller.startScroll(getScrollX(), 0, delta, 0, 1500);        invalidate();        currentScreenIndex = whichScreen;    }    private void snapToDestination() {        final int x = getScrollX();        final int screenWidth = getWidth();        scrollToScreen((x + (screenWidth / 2)) / screenWidth);    }    public int getCurrentScreenIndex() {        return currentScreenIndex;    }    public void startScroll() {        autoScroll = true;        handler.sendEmptyMessageDelayed(currentWhat, scrollTime);    }    public boolean isScrolling() {        return autoScroll;    }    public void stopScroll() {        autoScroll = false;        currentWhat++;    }    @Override    protected void finalize() throws Throwable {        Log.e("TAG", "finalize===");        super.finalize();    }    public OnItemClickListener getOnItemClickListener() {        return onItemClickListener;    }    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {        this.onItemClickListener = onItemClickListener;    }    public interface OnItemClickListener {        public void onClick(int index, View childview);    }    // OnClickListener onclick;}
第二步：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical" ><com.example.example.BannerLayoutandroid:id="@+id/layout_banner"android:layout_width="match_parent"android:layout_height="wrap_content" ><ImageViewandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:adjustViewBounds="true"android:src="@drawable/gsydgsdfasdqwf" /><ImageViewandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:adjustViewBounds="true"android:src="@drawable/hsfttyodfsd" /><ImageViewandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:adjustViewBounds="true"android:src="@drawable/tsdssbd" /><ImageViewandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:adjustViewBounds="true"android:src="@drawable/sdfdsf" /></com.example.example.BannerLayout></LinearLayout>

第三步：

package com.example.example;import android.os.Bundle;import android.app.Activity;public class MainActivity extends Activity {    private BannerLayout banner;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        banner = (BannerLayout) findViewById(R.id.layout_banner);    }    @Override    protected void onPause() {        banner.stopScroll();        super.onPause();    }    @Override    protected void onRestart() {        if (!banner.isScrolling())            banner.startScroll();        super.onRestart();    }    @Override    protected void onResume() {        if (!banner.isScrolling())            banner.startScroll();        super.onResume();    }    @Override    protected void onStop() {        banner.stopScroll();        super.onStop();    }    @Override    protected void onDestroy() {        banner.stopScroll();        super.onDestroy();    }}

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