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Android仿百度图片查看功能

时间：2020-12-25 12:16:37 | 栏目：Android代码 | 点击：次

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：

 

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