初学Android,图形图像之使用Bitmap和BitmapFactory(二十四)

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Bitmap代表一张位图，BitmapDrawable里封装的图片就是一个Bitmap对象．把Bitmap对象包装成BitmapDrawable对象，可以调用Bitmapdrawable的构造器

BitmapDrawable drawable = new BitmapDrawable(bitmap);

如果要获取BitmapDrawable所包装的bitmap对象,可以调用getBitmap()方法

Bitmap bitmap = drawable.getBitmap();

如果需要访问其它存储路径的图片,需要借助于BitmapFactory来解析,创建Bitmap对象

下面制作一个assets/文件夹下图片的图片查看器，在assets下随便放几张图像文件

class="language-java">package WangLi.Graphics.BitmapTest;

import java.io.IOException;
import java.io.InputStream;

import class="tags" href="/tags/ANDROID.html" title=android>android.app.Activity;
import class="tags" href="/tags/ANDROID.html" title=android>android.content.res.AssetManager;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.BitmapFactory;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.drawable.BitmapDrawable;
import class="tags" href="/tags/ANDROID.html" title=android>android.os.Bundle;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.View;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.View.OnClickListener;
import class="tags" href="/tags/ANDROID.html" title=android>android.widget.Button;
import class="tags" href="/tags/ANDROID.html" title=android>android.widget.ImageView;

public class BitmapTest extends Activity {
    /** Called when the activity is first created. */
	String[] class="tags" href="/tags/IMAGE.html" title=image>images = class="tags" href="/tags/NULL.html" title=null>null;
	AssetManager assets = class="tags" href="/tags/NULL.html" title=null>null;
	int currentImg = 0;
	ImageView class="tags" href="/tags/IMAGE.html" title=image>image;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        class="tags" href="/tags/IMAGE.html" title=image>image = (ImageView)findViewById(R.id.class="tags" href="/tags/IMAGE.html" title=image>image);
        try
        {
        	assets = getAssets();
        	//获取/assets/目录下所有文件
        	class="tags" href="/tags/IMAGE.html" title=image>images = assets.list("");
        }
        catch(IOException e)
        {
        	e.printStackTrace();
        }
        //获取bn按钮
        final Button next = (Button)findViewById(R.id.next);
        //为bn按钮绑定事件监听器,该监听器将会查看下一张图片
        next.setOnClickListener(new OnClickListener(){
        	public void onClick(View sources)
        	{
        		//如果发生数组越界
        		if(currentImg >= class="tags" href="/tags/IMAGE.html" title=image>images.length)
        		{
        			currentImg = 0;
        		}
        		//找到下一个图片文件
        		while(!class="tags" href="/tags/IMAGE.html" title=image>images[currentImg].endsWith(".png")
        				&& !class="tags" href="/tags/IMAGE.html" title=image>images[currentImg].endsWith(".jpg")
        				&& !class="tags" href="/tags/IMAGE.html" title=image>images[currentImg].endsWith(".gif"))
        		{
        			currentImg++;
        			//如果已发生数组越界
        			if(currentImg >= class="tags" href="/tags/IMAGE.html" title=image>images.length)
        			{
        				currentImg = 0;
        			}
        		}
        		InputStream assetFile = class="tags" href="/tags/NULL.html" title=null>null;
        		try
        		{
        			//打开指定的资源对应的输入流
        			assetFile = assets.open(class="tags" href="/tags/IMAGE.html" title=image>images[currentImg++]);
        		}
        		catch(IOException e)
        		{
        			e.printStackTrace();
        		}
        		BitmapDrawable bitmapDrawable = (BitmapDrawable)class="tags" href="/tags/IMAGE.html" title=image>image.getDrawable();
        		//如果图片还未回收,先强制回收该图片　
        		if(bitmapDrawable!=class="tags" href="/tags/NULL.html" title=null>null &&
        				!bitmapDrawable.getBitmap().isRecycled())
        		{
        			bitmapDrawable.getBitmap().recycle();
        		}
        		//改变ImageView显示的图片
        		class="tags" href="/tags/IMAGE.html" title=image>image.setImageBitmap(BitmapFactory.decodeStream(assetFile));
        	}
        });
    }
}