android 瀑布流原理及執行個體

最近發現瀑布流這個展現形式很是熱門，於是就研究著看看，結果發現瀑布流其實也很簡單，並不是那麼複雜。先看代碼，然後再解釋

先看圖

<?xml version="1.0" encoding="utf-8"?><ScrollView xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent" >    <LinearLayout        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:orientation="horizontal" >        <LinearLayout            android:id="@+id/layout01"                android:orientation="vertical"            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:layout_weight="1" >        </LinearLayout>        <LinearLayout            android:id="@+id/layout02"            android:orientation="vertical"            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:layout_weight="1" >        </LinearLayout>    </LinearLayout></ScrollView>

這裡大家看的很清楚，就一個ScrollView和2個LinearLayout，最外面的那層linearlayout不用去管他。想必大家也明白了，這次我要做的瀑布流是只有2列。ScrollView的作用其實就是讓這個瀑布具有滾動的作用！

下面來看代碼

代碼沒什麼難度，我就不解釋了。大家自己看吧，我傳上完整的執行個體代碼

package com.pb.main;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.drawable.BitmapDrawable;import android.graphics.drawable.Drawable;import android.os.AsyncTask;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.view.ViewGroup.LayoutParams;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.Toast;public class TestPbActivity extends Activity{    /** Called when the activity is first created. */    private LinearLayout layout01;    private LinearLayout layout02;    private Drawable[] drawables;    @Override    public void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        layout01 = (LinearLayout) findViewById(R.id.layout01);        layout02 = (LinearLayout) findViewById(R.id.layout02);        String[] imagePathStr = { "http://www.cf69.com/Upfiles/BeyondPic/2010-08/20108175740983313.jpg",                "http://www.syfff.com/UploadFile/pic/2008122163204.jpg", "http://pic.newssc.org/0/10/34/32/10343297_564251.jpg",                "http://ent.hangzhou.com.cn/images/20090311/zym2009031323.jpg", "http://a4.att.hudong.com/86/60/01300000013093119087608457965.jpg",                "http://file.sdteacher.gov.cn/upload/gz0901/images/0907/22/110437191.jpg",                "http://www.fun9.cn/uploadfile/starpic/uploadpics/200910/20091008090155126.jpg",                "http://img3.yxlady.com/yl/UploadFiles_5361/20110820/20110820120609469.jpg",                "http://news.sznews.com/content/images/site3/20070827/001558d90baa083c6da20d.jpg", "http://henan.sinaimg.cn/cr/2010/0824/2297073692.jpg",                "http://www.cf69.com/Upfiles/BeyondPic/2010-08/20108175740983313.jpg", "http://www.syfff.com/UploadFile/pic/2008122163204.jpg",                "http://pic.newssc.org/0/10/34/32/10343297_564251.jpg", "http://ent.hangzhou.com.cn/images/20090311/zym2009031323.jpg",                "http://a4.att.hudong.com/86/60/01300000013093119087608457965.jpg", "http://file.sdteacher.gov.cn/upload/gz0901/images/0907/22/110437191.jpg",                "http://www.fun9.cn/uploadfile/starpic/uploadpics/200910/20091008090155126.jpg",                "http://img3.yxlady.com/yl/UploadFiles_5361/20110820/20110820120609469.jpg",                "http://news.sznews.com/content/images/site3/20070827/001558d90baa083c6da20d.jpg", "http://henan.sinaimg.cn/cr/2010/0824/2297073692.jpg" };        // new LoadImageViews().execute(imagePathStr);        int j = 0;        for (int i = 0; i < imagePathStr.length; i++)        {            addBitMapToImage(imagePathStr[i], j, i);            j++;            if (j >= 2)            {                j = 0;            }        }    }    // 添加imageview 到layout    public void addBitMapToImage(String imagePath, int j, int i)    {        ImageView imageView = new ImageView(this);        imageView.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));        new ImageDownLoadAsyncTask(this,imagePath, imageView).execute((Void)null);        imageView.setTag(i);        if (j == 0)        {            layout01.addView(imageView);        } else if (j == 1)        {            layout02.addView(imageView);        }        imageView.setOnClickListener(new OnClickListener()        {            @Override            public void onClick(View v)            {                Toast.makeText(TestPbActivity.this, "您點擊了" + v.getTag() + "個Item", Toast.LENGTH_SHORT).show();            }        });    }}

/** * 非同步下載圖片 *  * @author sy *  */public class ImageDownLoadAsyncTask extends AsyncTask<Void, Void, Drawable>{    private String imagePath;    private View imageView;    private static final String ALBUM_PATH = "/sdcard/pb";    ProgressDialog progressDialog;    private Context context;    /**     * 構造方法     *      * @param context     * @param imagePath     * @param imageView     */    public ImageDownLoadAsyncTask(Context context, String imagePath, View imageView)    {        this.imagePath = imagePath;        this.imageView = imageView;        this.context = context;    }    @Override    protected Drawable doInBackground(Void... params)    {        // TODO Auto-generated method stub        String filePath = ALBUM_PATH + imagePath.substring(imagePath.lastIndexOf("/"));        File mfile = new File(filePath);        if (mfile.exists())        {// 若該檔案存在            Bitmap bm = BitmapFactory.decodeFile(filePath);            BitmapDrawable bd = new BitmapDrawable(bm);            return bd;        } else        {            URL url;            try            {                url = new URL(imagePath);                HttpURLConnection conn = (HttpURLConnection) url.openConnection();                conn.setDoInput(true);                conn.connect();                InputStream inputStream = conn.getInputStream();                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);                BitmapDrawable bd = new BitmapDrawable(bitmap);                saveFile(bd, imagePath.substring(imagePath.lastIndexOf("/")));                return bd;            } catch (MalformedURLException e)            {                e.printStackTrace();            } catch (IOException e)            {                e.printStackTrace();            }        }        return null;    }    @Override    protected void onPostExecute(Drawable drawable)    {        // TODO Auto-generated method stub        super.onPostExecute(drawable);        if (drawable != null)        {            imageView.setBackgroundDrawable(drawable);        }        progressDialog.dismiss();    }    @Override    protected void onPreExecute()    {        // TODO Auto-generated method stub        super.onPreExecute();        progressDialog = ProgressDialog.show(context, "", "正在下載圖片，請售後");    }    /**     * 將圖片存入SD卡     *      * @param drawable     * @param fileName     * @throws IOException     * @author sy     */    public void saveFile(Drawable drawable, String fileName) throws IOException    {        File dirFile = new File(ALBUM_PATH);        if (!dirFile.exists())        {            dirFile.mkdirs();        }        File myCaptureFile = new File(ALBUM_PATH + fileName);        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(myCaptureFile));        BitmapDrawable bd = (BitmapDrawable) drawable;        Bitmap bm = bd.getBitmap();        bm.compress(Bitmap.CompressFormat.JPEG, 80, bos);        bos.flush();        bos.close();    }}

哎，不知道部落格園怎麼上傳附近。。糾結。