Android仿百度图片查看功能

概述我们知道，进入百度图片后，输入一个关键字后，首先看到的是很多缩略图，当我们点击某张缩略图时，我们就可以进入到大图显示页面，在大图显示页面，中包含了一个图片画廊，同时当前大图为刚刚我们点击的那张图片。现

我们知道，进入百度图片后，输入一个关键字后，首先看到的是很多缩略图，当我们点击某张缩略图时，我们就可以进入到大图显示页面，在大图显示页面，中包含了一个图片画廊，同时当前大图为刚刚我们点击的那张图片。现在我们看看在AndroID中如何实现类似的效果： 

首先，我们需要有一个控件来显示缩略图，这里没有什么比GrIDVIEw更加合适了。 

配置文件如下： 

<?xml version="1.0" enCoding="utf-8"?> <linearLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"   androID:orIEntation="vertical"   androID:layout_wIDth="fill_parent"   androID:layout_height="fill_parent"   >   <GrIDVIEw     androID:ID="@+ID/vIEw_photos"      androID:layout_wIDth="fill_parent"      androID:layout_height="fill_parent"      androID:layout_margintop="10dp"      androID:columnWIDth="100dp"      androID:numColumns="auto_fit"      androID:horizontalSpacing="5dp"      androID:verticalSpacing="5dp"      androID:ListSelector="@drawable/frame_select" /> </linearLayout> 

对于GrIDVIEw中每一项是一张缩略图，我们需要继承BaseAdapter，实现自己的一个GrIDImageAdapter，代码：

package com.liner.manager; import java.util.List; import com.liner.manager.adapter.GrIDImageAdapter; import androID.app.Activity; import androID.graphics.Bitmap; import androID.os.Bundle; import androID.vIEw.VIEw; import androID.Widget.AdapterVIEw; import androID.Widget.gallery; import androID.Widget.Imagebutton; import androID.Widget.AdapterVIEw.OnItemClickListener; public class galleryActivity extends Activity{      private Imagebutton currentimage;   private gallery gallery;      private int[] thumbIDs;   private int currentPos;      private Bitmap currentBitmap;      private List<Bitmap> bitmapCache;      public voID onCreate(Bundle savedInstanceState){     super.onCreate(savedInstanceState);     setContentVIEw(R.layout.gallery);          currentimage = (Imagebutton)this.findVIEwByID(R.ID.image_current);     gallery = (gallery)this.findVIEwByID(R.ID.image_gallery);     gallery.setonItemClickListener(galleryItemClickListener);     init();   }      private OnItemClickListener galleryItemClickListener = new OnItemClickListener() {     @OverrIDe     public voID onItemClick(AdapterVIEw<?> p,VIEw v,int position,long ID) {       // 点击事件       showCurrentimage(position);     }   };      private voID init(){     thumbIDs = this.getIntent().getIntArrayExtra("thumbIDs");     currentPos = this.getIntent().getIntExtra("currentPos",0);     //galleryIDs = this.getthumbnailIDs(currentPos); //当前的gallery里的图片信息     bitmapCache = BitmapUtils.querythumbnailListByIDs(this,thumbIDs);     GrIDImageAdapter adapter = new GrIDImageAdapter(this.getApplication(),bitmapCache);     gallery.setAdapter(adapter);     gallery.setSelection(currentPos);          showCurrentimage(currentPos);        }      private voID showCurrentimage(int position){          if(currentBitmap != null){       currentBitmap.recycle();     }          currentBitmap = BitmapUtils.queryImageBythumbnailID(galleryActivity.this,thumbIDs[position]);     if(currentBitmap != null){       currentimage.setimageBitmap(currentBitmap);     }else{       //什么都不做     }          //releaseBitmaps();      }      /**    * 将gallery当前可见的显示之前的3张，后3张缓存起来，其余的释放掉，这样是为了放置内存不够用    * 之所以前三张后三张，是为了gallery可以滑动的更加顺畅    */   private voID releaseBitmaps(){     int start = gallery.getFirstVisibleposition()-3; //缓存的起始位置     int end = gallery.getLastVisibleposition()+3; //缓存的结束位置          Bitmap delBitmap;     for(int i=0; i<start; i++){       delBitmap = bitmapCache.get(i);       if(delBitmap != null){         bitmapCache.remove(i);         delBitmap.recycle();       }     }     for(int i=end+1; i<bitmapCache.size(); i++){       delBitmap = bitmapCache.get(i);       if(delBitmap != null){         bitmapCache.remove(i);         delBitmap.recycle();       }     }   }      /**    * 获取当前位置的前三个ID和后三个ID    * @param position    * @return    */   private Integer[] getthumbnailIDs(int position){     Integer[] IDs = new Integer[]{0,0};     int currPos = 0;     //关于这里的处理，比较复杂     for(int i=3; i>0; i--){       if(position - i >= 0){         currPos = 3-i;         IDs[currPos] = thumbIDs[position-i];       }     }     IDs[++currPos] = thumbIDs[position]; //当前ID     //currgallerySelection = currPos;     //这样右边剩下的位置数就是7-currPos-1     for(int i=1; i<=6-currPos;i++){       if(position+i < thumbIDs.length){         IDs[currPos+i] = thumbIDs[position+i];       }     }          return IDs;   }   } 

然后，我们就可以在Activity中通过查询MediaStore的多媒体图片库来查询所有的图片的缩略图，缩略图所在的位置是：
MediaStore.Images.thumbnails。Activity代码如下：

package com.liner.manager; import java.util.ArrayList; import java.util.List; import com.liner.manager.adapter.GrIDImageAdapter; import androID.app.Activity; import androID.content.Intent; import androID.database.Cursor; import androID.graphics.Bitmap; import androID.graphics.BitmapFactory; import androID.net.Uri; import androID.os.Bundle; import androID.provIDer.MediaStore; import androID.vIEw.VIEw; import androID.Widget.Adapter; import androID.Widget.AdapterVIEw; import androID.Widget.GrIDVIEw; import androID.Widget.Toast; public class MainActivity extends Activity {    private GrIDVIEw photoVIEw;   private GrIDImageAdapter imageAdapter;      private Cursor cursor;    private int[] thumbIDs;      @OverrIDe   public voID onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentVIEw(R.layout.main);          photoVIEw = (GrIDVIEw)this.findVIEwByID(R.ID.vIEw_photos);     photoVIEw.setonItemClickListener(photoClickListener);          //showImages();     showthumbnails();   }         private voID showthumbnails(){          cursor = BitmapUtils.querythumbnails(this);     if(cursor.movetoFirst()){       List<Bitmap> bitmaps = new ArrayList<Bitmap>();       thumbIDs = new int[cursor.getCount()];       for(int i=0; i<cursor.getCount();i++){         cursor.movetoposition(i);         String currPath = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.thumbnails.DATA));         thumbIDs[i] = cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Images.thumbnails._ID));         Bitmap b = BitmapUtils.decodeBitmap(currPath,100,100);         bitmaps.add(b);       }       imageAdapter = new GrIDImageAdapter(this.getApplication(),bitmaps);       photoVIEw.setAdapter(imageAdapter);     }   }      private AdapterVIEw.OnItemClickListener photoClickListener = new AdapterVIEw.OnItemClickListener() {     @OverrIDe     public voID onItemClick(AdapterVIEw<?> p,long ID) {       //点击某张缩略图时，转到图片显示界面            Intent intent = new Intent();       intent.setClass(MainActivity.this,galleryActivity.class);       intent.putExtra("thumbIDs",thumbIDs);       intent.putExtra("currentPos",position);       startActivity(intent);     }   };    } 

注意到，我们记录了，所有缩略图对应的ID号，和当前的用户选择的位置，然后通过Intent传递到第二个展示界面。第二个界面的布局文件如下：我们用了一个gallery和一个Imagebutton来实现

<?xml version="1.0" enCoding="utf-8"?> <linearLayout  xmlns:androID="http://schemas.androID.com/apk/res/androID"  androID:layout_wIDth="fill_parent"  androID:layout_height="fill_parent"  androID:orIEntation="vertical">   <gallery     androID:ID="@+ID/image_gallery"      androID:layout_wIDth="fill_parent"      androID:layout_height="100dp"      />   <Imagebutton     androID:ID="@+ID/image_current"      androID:layout_wIDth="fill_parent"      androID:layout_height="fill_parent"      androID:padding="10dp"      androID:layout_margintop="10dp"      /> </linearLayout> 

然后，对应的Activity如下：

package com.liner.manager; import java.util.List; import com.liner.manager.adapter.GrIDImageAdapter; import androID.app.Activity; import androID.graphics.Bitmap; import androID.os.Bundle; import androID.vIEw.VIEw; import androID.Widget.AdapterVIEw; import androID.Widget.gallery; import androID.Widget.Imagebutton; import androID.Widget.AdapterVIEw.OnItemClickListener; public class galleryActivity extends Activity{      private Imagebutton currentimage;   private gallery gallery;      private int[] thumbIDs;   private int currentPos;      private Bitmap currentBitmap;      private List<Bitmap> bitmapCache;      public voID onCreate(Bundle savedInstanceState){     super.onCreate(savedInstanceState);     setContentVIEw(R.layout.gallery);          currentimage = (Imagebutton)this.findVIEwByID(R.ID.image_current);     gallery = (gallery)this.findVIEwByID(R.ID.image_gallery);     gallery.setonItemClickListener(galleryItemClickListener);     init();   }      private OnItemClickListener galleryItemClickListener = new OnItemClickListener() {     @OverrIDe     public voID onItemClick(AdapterVIEw<?> p,thumbIDs[position]);     if(currentBitmap != null){       currentimage.setimageBitmap(currentBitmap);     }else{       //什么都不做     }          //releaseBitmaps();      }    } 

可以看到，当用户点击gallery中某一项时，触发onItemClick事件，在其中，我们通过根据该缩略图对应的Image_ID来从MediaStore.Images.Media中查询该缩略图对应的大图。并在Imagebutton中显示。 

这里当图片很多时，可能会出现内存溢出，为了避免这种情况，可以更加gallery的特点，使用缓存。保存当前可见的缩略图的前三个到后三个。其余的全部recycle。当用户点击gallery的时候，在判断当前的位置，如果大于或小于某个值时，则重新更新缓存。这样保证内存中的缩略图的个数总是6+gallery.getLastVisibleposition-gallery.getFirstVisibleposition个。其实这就是浮动缓存窗口，一个固定大小窗口在整个坐标（全部缩略图）上游动。这里没有实现，以后待续。 

同时，你可能已经注意到，程序中使用到了一个BitmapUtils类，这个类是封装了一系列对查询图片，并将其解析为Bitmap的类。 

代码如下：

package com.liner.manager; import java.util.ArrayList; import java.util.List; import androID.app.Activity; import androID.database.Cursor; import androID.graphics.Bitmap; import androID.graphics.BitmapFactory; import androID.provIDer.MediaStore; import androID.util.Log; public final class BitmapUtils {            public static Bitmap decodeBitmap(String path,int displayWIDth,int displayHeight){     BitmapFactory.Options op = new BitmapFactory.Options();     op.inJustDecodeBounds = true;     Bitmap bmp = BitmapFactory.decodefile(path,op); //获取尺寸信息     //获取比例大小     int wRatio = (int)Math.ceil(op.outWIDth/(float)displayWIDth);     int hRatio = (int)Math.ceil(op.outHeight/(float)displayHeight);     //如果超出指定大小，则缩小相应的比例     if(wRatio > 1 && hRatio > 1){       if(wRatio > hRatio){         op.inSampleSize = wRatio;       }else{         op.inSampleSize = hRatio;       }     }     op.inJustDecodeBounds = false;     bmp = BitmapFactory.decodefile(path,op);     return Bitmap.createScaledBitmap(bmp,displayWIDth,displayHeight,true);   }      /**    * 采用复杂计算来决定缩放    * @param path    * @param maxImageSize    * @return    */   public static Bitmap decodeBitmap(String path,int maxImageSize){     BitmapFactory.Options op = new BitmapFactory.Options();     op.inJustDecodeBounds = true;     Bitmap bmp = BitmapFactory.decodefile(path,op); //获取尺寸信息     int scale = 1;     if(op.outWIDth > maxImageSize || op.outHeight > maxImageSize){       scale = (int)Math.pow(2,(int)Math.round(Math.log(maxImageSize/(double)Math.max(op.outWIDth,op.outHeight))/Math.log(0.5)));     }     op.inJustDecodeBounds = false;     op.inSampleSize = scale;     bmp = BitmapFactory.decodefile(path,op);     return bmp;      }         public static Cursor querythumbnails(Activity context){     String[] columns = new String[]{         MediaStore.Images.thumbnails.DATA,MediaStore.Images.thumbnails._ID,MediaStore.Images.thumbnails.IMAGE_ID     };     return context.managedquery(MediaStore.Images.thumbnails.EXTERNAL_CONTENT_URI,columns,null,MediaStore.Images.thumbnails.DEFAulT_SORT_ORDER);   }      public static Cursor querythumbnails(Activity context,String selection,String[] selectionArgs){     String[] columns = new String[]{         MediaStore.Images.thumbnails.DATA,selection,selectionArgs,MediaStore.Images.thumbnails.DEFAulT_SORT_ORDER);      }      public static Bitmap querythumbnailByID(Activity context,int thumbID){     String selection = MediaStore.Images.thumbnails._ID + " = ?";     String[] selectionArgs = new String[]{       thumbID+""      };     Cursor cursor = BitmapUtils.querythumbnails(context,selectionArgs);          if(cursor.movetoFirst()){       String path = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.thumbnails.DATA));       cursor.close();       return BitmapUtils.decodeBitmap(path,100);     }else{       cursor.close();       return null;     }   }      public static Bitmap[] querythumbnailsByIDs(Activity context,Integer[] thumbIDs){     Bitmap[] bitmaps = new Bitmap[thumbIDs.length];     for(int i=0; i<bitmaps.length; i++){       bitmaps[i] = BitmapUtils.querythumbnailByID(context,thumbIDs[i]);     }          return bitmaps;   }      /**    * 获取全部    * @param context    * @return    */   public static List<Bitmap> querythumbnailList(Activity context){     List<Bitmap> bitmaps = new ArrayList<Bitmap>();     Cursor cursor = BitmapUtils.querythumbnails(context);     for(int i=0; i<cursor.getCount(); i++){       cursor.movetoposition(i);       String path = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.thumbnails.DATA));       Bitmap b = BitmapUtils.decodeBitmap(path,100);       bitmaps.add(b);     }     cursor.close();     return bitmaps;   }      public static List<Bitmap> querythumbnailListByIDs(Activity context,int[] thumbIDs){     List<Bitmap> bitmaps = new ArrayList<Bitmap>();     for(int i=0; i<thumbIDs.length; i++){       Bitmap b = BitmapUtils.querythumbnailByID(context,thumbIDs[i]);       bitmaps.add(b);     }          return bitmaps;   }        public static Cursor queryImages(Activity context){     String[] columns = new String[]{         MediaStore.Images.Media._ID,MediaStore.Images.Media.DATA,MediaStore.Images.Media.disPLAY_name     };     return context.managedquery(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,MediaStore.Images.Media.DEFAulT_SORT_ORDER);   }      public static Cursor queryImages(Activity context,String[] selectionArgs){     String[] columns = new String[]{         MediaStore.Images.Media._ID,MediaStore.Images.Media.DEFAulT_SORT_ORDER);       }      public static Bitmap queryImageByID(Activity context,int imageID){     String selection = MediaStore.Images.Media._ID + "=?";     String[] selectionArgs = new String[]{         imageID + ""     };     Cursor cursor = BitmapUtils.queryImages(context,selectionArgs);     if(cursor.movetoFirst()){       String path = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA));       cursor.close();       //return BitmapUtils.decodeBitmap(path,260,260);       return BitmapUtils.decodeBitmap(path,220); //看看和上面这种方式的差别,看了，差不多     }else{       cursor.close();       return null;     }   }      /**    * 根据缩略图的ID获取对应的大图    * @param context    * @param thumbID    * @return    */   public static Bitmap queryImageBythumbnailID(Activity context,Integer thumbID){          String selection = MediaStore.Images.thumbnails._ID + " = ?";     String[] selectionArgs = new String[]{       thumbID+""      };     Cursor cursor = BitmapUtils.querythumbnails(context,selectionArgs);          if(cursor.movetoFirst()){       int imageID = cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Images.thumbnails.IMAGE_ID));       cursor.close();       return BitmapUtils.queryImageByID(context,imageID);           }else{       cursor.close();       return null;     }   } } 

这样就实现了，类似百度图片浏览的效果。效果图如下：

 

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持编程小技巧。

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