android加载大图片

Gallery配合ImageSwitcher加载大图片展示

1.获得屏幕的宽高信息

WindowManager wm = getWindowManager();
int screenWidth = wm.getDefaultDisplay().getWidth();
int screenHeight = wm.getDefaultDisplay().getHeight();

2.得到图片的宽高

BitmapFactory.Options opt = new BitmapFactory.Options();// 解析位图的附加条件
opt.inJustDecodeBounds = true; // 不解析真实的位图，只是获取这个位图的头文件信息
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), imageResourceIds[position],opt); 
		
int bitmapWidth = opt.outWidth;
int bitmapHeight = opt.outHeight;

3.缩放比例

int scale = 1;
if(dx>dy&&dy>1) {
	System.out.println("按照水平方向缩放，缩放比例是：" + dx);
	scale = dx;
}
		
if(dy>dx&&dx>1) {
	System.out.println("按照竖直方向缩放，缩放比例是：" + dy);
	scale = dy;
}

// 4.缩放图片加载到内存 

opt.inSampleSize = scale; 
opt.inJustDecodeBounds = false; // 真正的去解析位图
bitmap = BitmapFactory.decodeResource(getResources(), imageResourceIds[position],opt);

demo实现效果：

自己mx4 pro拍的图片。。。当然酷酷的华哥不是自己拍的。。。

代码展示：

MainActivity .java

package com.example.imageswitcher;


import java.io.InputStream;


import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.graphics.Point;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.ViewSwitcher.ViewFactory;




public class MainActivity extends Activity {


	private ImageSwitcher imageSwitcher;
	private Gallery gallery;
	 // 准备数据
    private int [] imageResourceIds = {
    		R.drawable.m1,
    		R.drawable.m2,
    		R.drawable.m3,
    		R.drawable.m4
    };
	
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        
        imageSwitcher = (ImageSwitcher) findViewById(R.id.imageSwitcher);
        gallery = (Gallery) findViewById(R.id.gallery);
        
        // 1.给gallery设置图片 需要一个适配器
        gallery.setAdapter(new MyAdapter(imageResourceIds));
        // 这样的时候抛空指针异常了  原因是：imageSwitcher图片切换器，在使用时，需要去设置创建View对象的工厂类
        // 给ImageSwitcher设置一个工厂类，工厂类给ImageSwitcher创建一个对象
        imageSwitcher.setFactory(new MyViewFactory());
        
        // 设置切换图片时的动画效果
        // 进
        Animation inAnimation = AnimationUtils.loadAnimation(this, android.R.anim.fade_in);
        imageSwitcher.setInAnimation(inAnimation);
        // 出
        Animation outAnimation = AnimationUtils.loadAnimation(this, android.R.anim.fade_out);
        imageSwitcher.setOutAnimation(outAnimation);
        
        BitmapDrawable bd=new BitmapDrawable(getmBitmap(0));
        imageSwitcher.setImageDrawable(bd);
        
        gallery.setOnItemClickListener(new OnItemClickListener() {
			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				// 把点击的图片资源id设置给ImageSwitcher
				BitmapDrawable bd=new BitmapDrawable(getmBitmap(position));
		        imageSwitcher.setImageDrawable(bd);
			}
		});
    }
    
    class MyViewFactory implements ViewFactory {
    	/**
    	 * 创建一个对象返回给ImageSwitcher
    	 */
		@Override
		public View makeView() {
			ImageView iv = new ImageView(MainActivity.this);
			return iv;
		}
    }
    
    /**
	 * 给imageView设置图片
	 * @return
	 */
	public Bitmap getmBitmap(int position) {
		// 1.得到屏幕的宽高信息
		WindowManager wm = getWindowManager();
//		Point outSize = new Point();
//		wm.getDefaultDisplay().getSize(outSize);
		int screenWidth = wm.getDefaultDisplay().getWidth();
		int screenHeight = wm.getDefaultDisplay().getHeight();
		System.out.println("屏幕宽高：" + screenWidth + "-" + screenHeight);
		
		// 2.得到图片的宽高
		
//		iv.setImageResource(imageResIDs[position]);
		
		BitmapFactory.Options opt = new BitmapFactory.Options();// 解析位图的附加条件
		opt.inPreferredConfig = Bitmap.Config.ALPHA_8;
//		opt.inPurgeable = true;
//		opt.inInputShareable = true;
		opt.inJustDecodeBounds = true; // 不解析真是的位图，只是获取这个位图的头文件信息
		Bitmap bitmap = BitmapFactory.decodeResource(getResources(), imageResourceIds[position],opt); 
		
		int bitmapWidth = opt.outWidth;
		int bitmapHeight = opt.outHeight;
		System.out.println("图片宽高：" + bitmapWidth + bitmapHeight);
		
		int dx = bitmapWidth / screenWidth;
		int dy = bitmapHeight / screenHeight;
		
		int scale = 1;
		
		if(dx>dy&&dy>1) {
			System.out.println("按照水平方向缩放，缩放比例是：" + dx);
			scale = dx;
		}
		
		if(dy>dx&&dx>1) {
			System.out.println("按照竖直方向缩放，缩放比例是：" + dy);
			scale = dy;
		}
		
		// 4.缩放图片加载到内存 
		opt.inSampleSize = scale; 
		opt.inJustDecodeBounds = false; // 真正的去解析位图
		
		bitmap = BitmapFactory.decodeResource(getResources(), imageResourceIds[position],opt);    
//		iv.setImageBitmap(bitmap2);
		return bitmap;
	}
    
    class MyAdapter extends BaseAdapter {


    	private int []imageResIDs;
    	
		public MyAdapter(int [] imageResIDs) {
			super();
			this.imageResIDs = imageResIDs;
		}
		
		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			ImageView iv = null;
			if(convertView == null) {
				// 当前内存中没有缓存对象，应该自己创建一个新的
				iv = new ImageView(MainActivity.this);
			} else {
			    // 当前内存中有缓存对象，应该使用缓存对象
				iv = (ImageView) convertView;
			}
//			setImageView();
			iv.setImageBitmap(getmBitmap(position));
//			InputStream is = MainActivity.this.getResources().openRawResource(imageResIDs[position]);
//			Bitmap bitmap = BitmapFactory.decodeStream(is);
//			iv.setImageResource(bitmap);
//			iv.setImageBitmap(bitmap);
//			if(!bitmap.isRecycled() ){
//				bitmap.recycle();   //回收图片所占的内存         
//		        System.gc();  //提醒系统及时回收
//		    }
			// 设置图片的宽高比和当前控件一样
			iv.setAdjustViewBounds(true);
			// 设置图片一周圈的边距
			iv.setPadding(2, 2, 2, 2);
			iv.setBackgroundColor(Color.RED);
			return iv;
		}


		


		@Override
		public int getCount() {
			return imageResourceIds.length;
		}


		@Override
		public Object getItem(int position) {
			return imageResourceIds[position];
		}


		@Override
		public long getItemId(int position) {
			return position;
		}


    }
}

activity_main.xml

<LinearLayout 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:background="@android:color/black"
    android:orientation="vertical" >

	<ImageSwitcher 
	    android:id="@+id/imageSwitcher"
	    android:layout_width="fill_parent"
	    android:layout_height="0dip"
	    android:layout_weight="1"></ImageSwitcher>
	
	<Gallery 
	    android:id="@+id/gallery"
	    android:layout_marginTop="5dip"
	    android:layout_width="fill_parent"
	    android:layout_height="100dip"
	    android:spacing="20dip"></Gallery>
    
</LinearLayout>

完整源代码下载：http://download.youkuaiyun.com/detail/wang725/8836733