Android控件之ImageView探究

ImageView控件是一个图片控件，负责显示图片。

以下模拟手机图片查看器

目录结构

main.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent">
<ImageView android:id="@+id/imageView"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_gravity="center_horizontal"
 android:src="@drawable/p1"/>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="horizontal"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:layout_gravity="center_horizontal">
<Button android:id="@+id/previous"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="上一张"
 android:layout_gravity="center_horizontal"/>
<Button android:id="@+id/alpha_plus"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="透明度增加"
 android:layout_gravity="center_horizontal"/>
<Button android:id="@+id/alpha_minus"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="透明度减少"
 android:layout_gravity="center_horizontal"/>
<Button android:id="@+id/next"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="下一张"
 android:layout_gravity="center_horizontal"/>
</LinearLayout>
</LinearLayout>

ImageViewActivity类

package com.ljq.iv;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class ImageViewActivity extends Activity {
private ImageView imageView=null;
private Button previous=null;//上一张
 private Button next=null;//下一张
 private Button alpha_plus=null;//透明度增加
 private Button alpha_minus=null;//透明度减少
 private int currentImgId=0;//记录当前ImageView显示的图片id
 private int alpha=255;//记录ImageView的透明度
 int [] imgId = { //ImageView显示的图片数组
 R.drawable.p1, 
 R.drawable.p2,
 R.drawable.p3,
 R.drawable.p4,
 R.drawable.p5,
 R.drawable.p6,
 R.drawable.p7,
 R.drawable.p8,
 };

 @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
 setContentView(R.layout.main);

 imageView=(ImageView)findViewById(R.id.imageView);
 previous=(Button)findViewById(R.id.previous);
 next=(Button)findViewById(R.id.next);
 alpha_plus=(Button)findViewById(R.id.alpha_plus);
 alpha_minus=(Button)findViewById(R.id.alpha_minus);

 previous.setOnClickListener(listener);
 next.setOnClickListener(listener);
 alpha_plus.setOnClickListener(listener);
 alpha_minus.setOnClickListener(listener);
 }

private View.OnClickListener listener = new View.OnClickListener(){

public void onClick(View v) {
if(v==previous){
 currentImgId=(currentImgId-1+imgId.length)%imgId.length;
 imageView.setImageResource(imgId[currentImgId]);
 }
if(v==next){
 currentImgId=(currentImgId+1)%imgId.length;
 imageView.setImageResource(imgId[currentImgId]);
 }
if(v==alpha_plus){
 alpha+=10;
if(alpha>255){
 alpha=255;
 }
 imageView.setAlpha(alpha);
 }
if(v==alpha_minus){
 alpha-=10;
if(alpha<0){
 alpha=0;
 }
 imageView.setAlpha(alpha);
 }
 }

 };

}

运行结果