Android应用开发学习之图片切换器

作者：刘昊昱

博客：http://blog.****.net/liuhaoyutz

如果我们要实现类似Windows的照片查看器切换上一张下一张照片的效果，可以使用图片切换器ImageSwitcher，下面我们来看一个例子，其运行效果如下所示：

先来看主布局文件main.xml，其内容如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center"
    android:orientation="vertical" >

    <ImageSwitcher
		android:id="@+id/imageSwitcher"
		android:layout_width="300px"
		android:layout_height="300px"/>"

    <LinearLayout
        android:orientation="horizontal"
        android:gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:text="上一张"
    		android:id="@+id/button1"
    		android:layout_gravity="center"
    		android:layout_width="wrap_content"
    		android:layout_height="wrap_content"/>
        <Button
	    	android:text="下一张"
    		android:id="@+id/button2"
    		android:layout_gravity="center"
    		android:layout_width="wrap_content"
    		android:layout_height="wrap_content"/>
    </LinearLayout>

</LinearLayout>

下面来看主Activity文件，其内容如下：

package com.liuhaoyu;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup.LayoutParams;
import android.view.animation.AnimationUtils;
import android.widget.Button;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.ViewSwitcher.ViewFactory;

public class MainActivity extends Activity {
	private int[] imageId = new int[] { R.drawable.img01, R.drawable.img02,
			R.drawable.img03, R.drawable.img04, R.drawable.img05,
			R.drawable.img06, R.drawable.img07, R.drawable.img08};
	private int index = 0;
	private ImageSwitcher imageSwitcher;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        imageSwitcher = (ImageSwitcher) findViewById(R.id.imageSwitcher);
		imageSwitcher.setInAnimation(AnimationUtils.loadAnimation(this,
				android.R.anim.fade_in));
		imageSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,
				android.R.anim.fade_out));
		imageSwitcher.setFactory(new ViewFactory() {
			@Override
			public View makeView() {
				ImageView imageView = new ImageView(MainActivity.this);
				imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
				imageView.setLayoutParams(new ImageSwitcher.LayoutParams(
						LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
				return imageView;
			}
		});
		imageSwitcher.setImageResource(imageId[index]);

		Button previous = (Button) findViewById(R.id.button1);
		Button next = (Button) findViewById(R.id.button2);
		previous.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
					if (index > 0) {
						index--;
					} else {
						index = imageId.length - 1;
					}
				imageSwitcher.setImageResource(imageId[index]);
			}
		});
		next.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				if (index < imageId.length - 1) {
					index++;
				} else {
					index = 0;
				}
				imageSwitcher.setImageResource(imageId[index]);
			}
		});
    }
}