Android控制項之ImageView探究

ImageView控制項是一個圖片控制項，負責顯示圖片。

以下類比手機圖片查看器

目錄結構

main.xml布局檔案

<?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="上一張"
            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="透明度減少"
            android:layout_gravity="center_horizontal"/>
<Button android:id="@+id/next"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="下一張"
            android:layout_gravity="center_horizontal"/>
</LinearLayout>
</LinearLayout>

ImageViewActivity類

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;//上一張
    private Button next=null;//下一張
    private Button alpha_plus=null;//透明度增加
    private Button alpha_minus=null;//透明度減少
    private int currentImgId=0;//記錄當前ImageView顯示的圖片id
    private int alpha=255;//記錄ImageView的透明度
    int [] imgId = {            //ImageView顯示的圖片數組
            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);
            }
        }

    };

}

運行結果