Android仿百度图片查看功能

2019-10-22 18:20:19

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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[]{0,0,0,0,0,0,0};     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, View v, int position,         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, 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();      }    }

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, 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,         MediaStore.Images.Thumbnails._ID,         MediaStore.Images.Thumbnails.IMAGE_ID     };     return context.managedQuery(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, columns, 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,selection,selectionArgs);          if(cursor.moveToFirst()){       String path = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails.DATA));       cursor.close();       return BitmapUtils.decodeBitmap(path, 100, 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, 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, columns, null, null, MediaStore.Images.Media.DEFAULT_SORT_ORDER);   }      public static Cursor queryImages(Activity context, String selection, String[] selectionArgs){     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, columns, selection, selectionArgs, 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, selection, 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, selection, 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：

Android,图片查看