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Android仿百度圖片查看功能

我們知道，進(jìn)入百度圖片后，輸入一個(gè)關(guān)鍵字后，首先看到的是很多縮略圖，當(dāng)我們點(diǎn)擊某張縮略圖時(shí)，我們就可以進(jìn)入到大圖顯示頁面，在大圖顯示頁面，中包含了一個(gè)圖片畫廊，同時(shí)當(dāng)前大圖為剛剛我們點(diǎn)擊的那張圖片。現(xiàn)在我們看看在Android中如何實(shí)現(xiàn)類似的效果： 

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首先，我們需要有一個(gè)控件來顯示縮略圖，這里沒有什么比GridView更加合適了。 

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>

對(duì)于GridView中每一項(xiàng)是一張縮略圖，我們需要繼承BaseAdapter，實(shí)現(xiàn)自己的一個(gè)GridImageAdapter，代碼：

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) { 
      // 點(diǎn)擊事件 
      showCurrentImage(position); 
    } 
  }; 
   
  private void init(){ 
    thumbIds = this.getIntent().getIntArrayExtra("thumbIds"); 
    currentPos = this.getIntent().getIntExtra("currentPos",0); 
    //galleryIds = this.getThumbnailIds(currentPos); //當(dāng)前的gallery里的圖片信息 
    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();    
  } 
   
  /** 
   * 將Gallery當(dāng)前可見的顯示之前的3張，后3張緩存起來，其余的釋放掉，這樣是為了放置內(nèi)存不夠用 
   * 之所以前三張后三張，是為了Gallery可以滑動(dòng)的更加順暢 
   */ 
  private void releaseBitmaps(){ 
    int start = gallery.getFirstVisiblePosition()-3; //緩存的起始位置 
    int end = gallery.getLastVisiblePosition()+3; //緩存的結(jié)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(); 
      } 
    } 
  } 
   
  /** 
   * 獲取當(dāng)前位置的前三個(gè)Id和后三個(gè)Id 
   * @param position 
   * @return 
   */ 
  private Integer[] getThumbnailIds(int position){ 
    Integer[] ids = new Integer[]{0,0,0,0,0,0,0}; 
    int currPos = 0; 
    //關(guān)于這里的處理，比較復(fù)雜 
    for(int i=3; i>0; i--){ 
      if(position - i >= 0){ 
        currPos = 3-i; 
        ids[currPos] = thumbIds[position-i]; 
      } 
    } 
    ids[++currPos] = thumbIds[position]; //當(dāng)前Id 
    //currGallerySelection = currPos; 
    //這樣右邊剩下的位置數(shù)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，我們就可以在Activity中通過查詢MediaStore的多媒體圖片庫來查詢所有的圖片的縮略圖，縮略圖所在的位置是：
MediaStore.Images.Thumbnails。Activity代碼如下：

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) { 
      //點(diǎn)擊某張縮略圖時(shí)，轉(zhuǎn)到圖片顯示界面      
      Intent intent = new Intent(); 
      intent.setClass(MainActivity.this, GalleryActivity.class); 
      intent.putExtra("thumbIds", thumbIds); 
      intent.putExtra("currentPos", position); 
      startActivity(intent); 
    } 
  }; 
   
}

注意到，我們記錄了，所有縮略圖對(duì)應(yīng)的id號(hào)，和當(dāng)前的用戶選擇的位置，然后通過Intent傳遞到第二個(gè)展示界面。第二個(gè)界面的布局文件如下：我們用了一個(gè)Gallery和一個(gè)ImageButton來實(shí)現(xiàn)

<?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，對(duì)應(yīng)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) { 
      // 點(diǎn)擊事件 
      showCurrentImage(position); 
    } 
  }; 
   
  private void init(){ 
    thumbIds = this.getIntent().getIntArrayExtra("thumbIds"); 
    currentPos = this.getIntent().getIntExtra("currentPos",0); 
    //galleryIds = this.getThumbnailIds(currentPos); //當(dāng)前的gallery里的圖片信息 
    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，當(dāng)用戶點(diǎn)擊Gallery中某一項(xiàng)時(shí)，觸發(fā)onItemClick事件，在其中，我們通過根據(jù)該縮略圖對(duì)應(yīng)的Image_ID來從MediaStore.Images.Media中查詢?cè)摽s略圖對(duì)應(yīng)的大圖。并在ImageButton中顯示。 

這里當(dāng)圖片很多時(shí)，可能會(huì)出現(xiàn)內(nèi)存溢出，為了避免這種情況，可以更加Gallery的特點(diǎn)，使用緩存。保存當(dāng)前可見的縮略圖的前三個(gè)到后三個(gè)。其余的全部recycle。當(dāng)用戶點(diǎn)擊Gallery的時(shí)候，在判斷當(dāng)前的位置，如果大于或小于某個(gè)值時(shí)，則重新更新緩存。這樣保證內(nèi)存中的縮略圖的個(gè)數(shù)總是6+Gallery.getLastVisiblePosition-Gallery.getFirstVisiblePosition個(gè)。其實(shí)這就是浮動(dòng)緩存窗口，一個(gè)固定大小窗口在整個(gè)坐標(biāo)（全部縮略圖）上游動(dòng)。這里沒有實(shí)現(xiàn)，以后待續(xù)。 

同時(shí)，你可能已經(jīng)注意到，程序中使用到了一個(gè)BitmapUtils類，這個(gè)類是封裝了一系列對(duì)查詢圖片，并將其解析為Bitmap的類。 

代碼如下：

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); //獲取尺寸信息 
    //獲取比例大小 
    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，則縮小相應(yīng)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); 
  } 
   
  /** 
   * 采用復(fù)雜計(jì)算來決定縮放 
   * @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); //獲取尺寸信息 
    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; 
  } 
   
  /** 
   * 獲取全部 
   * @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); //看看和上面這種方式的差別,看了，差不多 
    }else{ 
      cursor.close(); 
      return null; 
    } 
  } 
   
  /** 
   * 根據(jù)縮略圖的Id獲取對(duì)應(yīng)的大圖 
   * @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; 
    } 
  } 
}

這樣就實(shí)現(xiàn)了，類似百度圖片瀏覽的效果。

以上就是本文的全部內(nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持創(chuàng)新互聯(lián)。

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