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() {@Overridepublic void onItemClick(AdapterView<?> parent, View view,int position, long id) {// 把点击的图片资源id设置给ImageSwitcherBitmapDrawable bd=new BitmapDrawable(getmBitmap(position));        imageSwitcher.setImageDrawable(bd);}});    }        class MyViewFactory implements ViewFactory {    /**     * 创建一个对象返回给ImageSwitcher     */@Overridepublic 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;}@Overridepublic 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;}@Overridepublic int getCount() {return imageResourceIds.length;}@Overridepublic Object getItem(int position) {return imageResourceIds[position];}@Overridepublic 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.csdn.net/detail/wang725/8836733

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