Android圖片瀏覽源碼解讀
Android手機(jī)操作系統(tǒng)的應(yīng)用方式靈活,簡單,深受廣大編程愛好者的喜愛。尤其是它的開源代碼,使得我們能夠方便的得到自己想要的功能需求。今天我們就為大家?guī)砹擞嘘P(guān)Android圖片瀏覽的相關(guān)方法。
首先是Android圖片瀏覽中l(wèi)ayout xml:
- < ?xml version="1.0" encoding="utf-8"?>
 - < RelativeLayout xmlns:android="http://schemas.Android.com/apk/res/Android"
 - Android:layout_width="fill_parent"
 - Android:layout_height="fill_parent">
 - < ImageSwitcher Android:id="@+id/switcher"
 - Android:layout_width="fill_parent"
 - Android:layout_height="fill_parent"
 - Android:layout_alignParentTop="true"
 - Android:layout_alignParentLeft="true"
 - />
 - < Gallery Android:id="@+id/gallery"
 - Android:background="#55000000"
 - Android:layout_width="fill_parent"
 - Android:layout_height="60dp"
 - Android:layout_alignParentBottom="true"
 - Android:layout_alignParentLeft="true"
 - Android:gravity="center_vertical"
 - Android:spacing="16dp"
 - />
 - < /RelativeLayout>
 
layout里面用到了前面所說的兩個控件,ImageSwitcher用啦顯示全圖,Gallery用來顯示縮略圖。著重看看ImageSwitcher,在ImageSwitcher1中需要實現(xiàn)ViewSwitcher.ViewFactory這個接口,這個接口里有個方法makeView,這樣就產(chǎn)生了用來顯示圖片的view. ImageSwitcher調(diào)用過程是這樣的,首先要有一個Factory為它提供一個View,然后ImageSwitcher就可以初始化各種資源了。注意在使用一個ImageSwitcher之前,一定要調(diào)用setFactory方法,要不setImageResource這個方法會報空指針異常。
下面是Android圖片瀏覽代碼:
- package com.zx.imageswitcher;
 - import Android.app.Activity;
 - import Android.content.Context;
 - 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 Android.widget.Gallery.LayoutParams;
 - public class ImageSwitcherTest extends Activity implements
 - AdapterView.OnItemSelectedListener, ViewSwitcher.ViewFactory{
 - private ImageSwitcher mSwitcher;
 - private Integer[] mThumbIds = {
 - R.drawable.sample_thumb_0, R.drawable.sample_thumb_1,
 - R.drawable.sample_thumb_2, R.drawable.sample_thumb_3,
 - R.drawable.sample_thumb_4, R.drawable.sample_thumb_5,
 - R.drawable.sample_thumb_6, R.drawable.sample_thumb_7};
 - private Integer[] mImageIds = {
 - R.drawable.sample_0, R.drawable.sample_1, R.drawable.sample_2,
 - R.drawable.sample_3, R.drawable.sample_4, R.drawable.sample_5,
 - R.drawable.sample_6, R.drawable.sample_7};
 - /** Called when the activity is first created. */
 - @Override
 - public void onCreate(Bundle savedInstanceState) {
 - super.onCreate(savedInstanceState);
 - setContentView(R.layout.main);
 - mSwitcher = (ImageSwitcher) findViewById(R.id.switcher);
 - mSwitcher.setFactory(this);
 - mSwitcher.setInAnimation(AnimationUtils.loadAnimation(this,
 - Android.R.anim.fade_in));
 - mSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,
 - Android.R.anim.fade_out));
 - Gallery g = (Gallery) findViewById(R.id.gallery);
 - g.setAdapter(new ImageAdapter(this));
 - g.setOnItemSelectedListener(this);
 - }
 - /*
 - * override for ViewSwitcher.ViewFactory#makeView()
 - */
 - public View makeView() {
 - ImageView i = new ImageView(this);
 - i.setBackgroundColor(0xFF000000);
 - i.setScaleType(ImageView.ScaleType.FIT_CENTER);
 - i.setLayoutParams(new ImageSwitcher.LayoutParams
 
(LayoutParams.FILL_PARENT,- LayoutParams.FILL_PARENT));
 - return i;
 - }
 - /*
 - * override for
 - * AdapterView.OnItemSelectedListener#onItemSelected()
 - */
 - public void onItemSelected(AdapterView parent,
 
View v, int position, long id) {- mSwitcher.setImageResource(mImageIds[position]);
 - }
 - /*
 - * override for AdapterView.OnItemSelectedListener
 
#onNothingSelected()- */
 - public void onNothingSelected(AdapterView< ?> arg0) {
 - // TODO Auto-generated method stub
 - }
 - public class ImageAdapter extends BaseAdapter {
 - public ImageAdapter(Context c) {
 - mContext = c;
 - }
 - public int getCount() {
 - return mThumbIds.length;
 - }
 - public Object getItem(int position) {
 - return position;
 - }
 - public long getItemId(int position) {
 - return position;
 - }
 - public View getView(int position, View convertView,
 
ViewGroup parent) {- ImageView i = new ImageView(mContext);
 - i.setImageResource(mThumbIds[position]);
 - i.setAdjustViewBounds(true);
 - i.setLayoutParams(new Gallery.LayoutParams(
 - LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
 - i.setBackgroundResource(R.drawable.picture_frame);
 - return i;
 - }
 - private Context mContext;
 - }
 - }
 
從Android圖片瀏覽的代碼中看到還實現(xiàn)了AdapterView.OnItemSelectedListener,這樣就需要重寫onItemSelected()方法,然后在該方法中:mSwitcher.setImageResource(mImageIds[position]);這樣就實現(xiàn)了圖片在ImageSwitcher中的切換。
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