Android控件之ImageView用法实例分析

<?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>

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);   }  } };}