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);

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>