Android 初学图片切换 Image switching and showing

本文介绍了一个使用Android开发的简单图片切换应用。应用采用ImageSwitcher和Gallery组件实现图片的淡入淡出效果及图片选择。文章详细展示了如何通过自定义Adapter来加载图片资源。

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今天用AS学做了一个简单的图片切换小程序

其中用到了一个ImageSwitcher的类通过设置一个ViewFactory工厂，实现其makeView()方法来创建显示图片的View。和和一个叫做“画廊类”的Gallery类，来陈列图片资源；

方法setImageResource用来显示指定的图片资源。

1.声明所需的变量private Gallery gallery;private ImageSwitcher imageSwitcher;将7张图片放入/res/drawable目录下，声明一个数组把图片资源放到数组里

private int[] res={R.drawable.grid_view_02,R.drawable.grid_view_03,R.drawable.grid_view_04,R.drawable.grid_view_05,R.drawable.grid_view_06,R.drawable.grid_view_12,R.drawable.grid_view_14};

2.MainActivity.java

package com.example.ch.imageswitchingandshowing;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AnimationUtils;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.ViewSwitcher;

import java.util.Iterator;

public class MainActivity extends AppCompatActivity {
    private Gallery gallery;
    private ImageSwitcher imageSwitcher;
    private int[] res={R.drawable.grid_view_02,R.drawable.grid_view_03,R.drawable.grid_view_04,
            R.drawable.grid_view_05,R.drawable.grid_view_06,R.drawable.grid_view_12,R.drawable.grid_view_14};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        gallery=(Gallery)findViewById(R.id.gallery);
        imageSwitcher=(ImageSwitcher)findViewById(R.id.imageSwitcher);
        //buju
        imageSwitcher.setFactory(new ViewSwitcher.ViewFactory() {
            @Override
            public View makeView() {
                ImageView imageView= new ImageView(MainActivity.this);
                imageView.setBackgroundColor(0xff000000);
                imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
                imageView.setLayoutParams(new ImageSwitcher.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                        ViewGroup.LayoutParams.MATCH_PARENT));
                return imageView;
            }
        });
        imageSwitcher.setInAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_in));//设置进入的动态效果，叠进
        imageSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_out));

//下面这一步是准备Gallery工作，获得信息。
        gallery.setAdapter(new BaseAdapter() {
            @Override

//获得<span style="font-family: 宋体;">gallery里的图片个数（item）</span>
            public int getCount() {
                return res.length;
            }

            @Override
            public Object getItem(int position) {

                return position;
            }

            @Override

<span style="color: rgb(51, 51, 51); font-family: 宋体; font-size: 14px; line-height: 28px; text-indent: 28px; background-color: rgb(249, 249, 249);">//至于getItemId(int position)，它返回的是该postion对应item的id</span>
            public long getItemId(int position) {
                return position;
            }

            @Override

//得到画廊中的一个图片
            public View getView(int position, View convertView, ViewGroup parent) {
                ImageView imageView = new ImageView(MainActivity.this);
                imageView.setLayoutParams(new Gallery.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                imageView.setAdjustViewBounds(true);
                imageView.setImageResource(res[position]);
                return imageView;
            }
        });

//选中画廊中的item监听事件
        gallery.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override

//选中了就将图片给到<span style="font-family: 宋体;">imageSwitcher中</span>
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                imageSwitcher.setImageResource(res[position]);
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });
    }
}

layout布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.ch.imageswitchingandshowing.MainActivity">

    <ImageSwitcher
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/imageSwitcher"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Gallery
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:id="@+id/gallery"
        android:spacing="20dp"//展览图片时，设置相邻图片的间距
        android:gravity="center_vertical"
        android:layout_alignBottom="@+id/imageSwitcher"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

</RelativeLayout>

托这两个控件时不要使这两者的区域有重叠部分。

效果如下所示：