ViewPager+Handler實現圖片自動輪播的效果

效果圖就不貼了，最下面有源碼，用AndroidStudio寫的。

分析來也就兩種狀態，暫停輪播和開始輪播，這裏爲了避免bug，有一個記錄頁號的TAG

佈局是最簡單的。只有一個viewpager，在V4包下面

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/ViewPager_vp"
android:layout_width="match_parent"
android:layout_height="match_parent">

</android.support.v4.view.ViewPager>

簡單的activity

package demo.viewpager;

import android.os.Bundle;
import android.os.Message;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;

import demo.viewpager.Utils.ViewPagerHandlerUtils;
import demo.viewpager.adapter.ViewPagerAdapter;

/**
 * Created by 12406 on 2016/1/16.
 */
public class ViewPagerActivity extends AppCompatActivity {


    private ViewPagerAdapter adapter;
    private ViewPager viewPager;
    private ViewPagerHandlerUtils handlerUtils;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_viewpager);
        viewPager = (ViewPager) findViewById(R.id.ViewPager_vp);

        init();
    }

    private void init() {
        handlerUtils = new ViewPagerHandlerUtils(viewPager);
        handlerUtils.sendEmptyMessageDelayed(handlerUtils.MSG_UPDATE, handlerUtils.MSG_DELAY);
        adapter = new ViewPagerAdapter(this);
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            }

            @Override
            public void onPageSelected(int position) {
                handlerUtils.sendMessage(Message.obtain(handlerUtils, handlerUtils.MSG_PAGE, position, 0));
            }

            @Override
            public void onPageScrollStateChanged(int state) {
                switch (state) {
                    case ViewPager.SCROLL_STATE_DRAGGING:
                        handlerUtils.sendEmptyMessage(handlerUtils.MSG_KEEP);
                        break;
                    case ViewPager.SCROLL_STATE_IDLE:
                        handlerUtils.sendEmptyMessageDelayed(handlerUtils.MSG_UPDATE,
                                handlerUtils.MSG_DELAY);
                }
            }
        });
    }
}

Adapter也是單獨寫的一個java類

package demo.viewpager.adapter;

import android.app.Activity;
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.Toast;

import demo.viewpager.R;

/**
 * Created by 12406 on 2016/1/16.
 */
public class ViewPagerAdapter extends PagerAdapter {
    private Activity activity;
    private int[] imager = new int[]{R.drawable.item1, R.drawable.item2, R.drawable.item3, R.drawable.item4, R.drawable.item5, R.drawable.item6};


    public ViewPagerAdapter(Activity activity) {
        this.activity = activity;
    }


    @Override
    public int getCount() {
        return Integer.MAX_VALUE;
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public void destroyItem(ViewGroup container, int position,
                            Object object) {
        container.removeView((View) object);
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        position %= imager.length;
        if (position < 0) {
            position = imager.length + position;
        }
        ImageView imageView = new ImageView(activity);
        imageView.setImageResource(imager[position]);
//        imageView.setScaleType(ImageView.ScaleType.FIT_XY);
        final int finalPosition = position;
        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(activity, "第" + finalPosition + "個被點擊了", Toast.LENGTH_SHORT).show();
            }
        });
        container.addView(imageView);
        return imageView;
    }


}

Handler爲了方便直接抽取出來寫一個工具類

package demo.viewpager.Utils;


import android.os.Handler;
import android.os.Message;
import android.support.v4.view.ViewPager;

public class ViewPagerHandlerUtils extends Handler {

    /**
     * 請求更新顯示的ImageView。
     */
    public static final int MSG_UPDATE = 1;
    /**
     * 請求暫停輪播。
     */
    public static final int MSG_KEEP = 2;
    /**
     * 請求恢復輪播。
     */
    public static final int MSG_BREAK = 3;
    /**
     * 記錄最新的頁號
     */
    public static final int MSG_PAGE = 4;

    //輪播間隔時間
    public static final long MSG_DELAY = 2000;

    private ViewPager mViewPager;
    private int currentItem = 0;

    public ViewPagerHandlerUtils(ViewPager viewPager) {
        mViewPager = viewPager;
    }

    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        if (mViewPager == null) {
            return;
        }
        if (hasMessages(MSG_UPDATE)) {
            removeMessages(MSG_UPDATE);
        }
        switch (msg.what) {
            case MSG_UPDATE:
                currentItem++;
                mViewPager.setCurrentItem(currentItem);
                sendEmptyMessageDelayed(MSG_UPDATE, MSG_DELAY);
                break;
            case MSG_KEEP:
                break;
            case MSG_BREAK:
                sendEmptyMessageDelayed(MSG_UPDATE, MSG_DELAY);
                break;
            case MSG_PAGE:
                currentItem = msg.arg1;
                break;
            default:
                sendEmptyMessageDelayed(MSG_UPDATE, MSG_DELAY);
                break;
        }
    }
}

代碼也是最基礎的一些東西，看起來也不費勁。

點擊下載源碼