Android仿百度图片查看功能

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：

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我们。