1 package com.don.waterfall_test;  2   3 import java.io.IOException;  4 import java.io.InputStream;  5 import java.util.ArrayList;  6 import java.util.Arrays;  7 import java.util.List;  8   9 import android.app.Activity; 10 import android.content.res.AssetManager; 11 import android.graphics.Bitmap; 12 import android.graphics.BitmapFactory; 13 import android.os.Bundle; 14 import android.view.Display; 15 import android.view.MotionEvent; 16 import android.view.View; 17 import android.view.View.OnTouchListener; 18 import android.widget.ImageView; 19 import android.widget.LinearLayout; 20 import android.widget.LinearLayout.LayoutParams; 21 import android.widget.ScrollView; 22  23 public class MainActivity extends Activity implements OnTouchListener { 24    private ScrollView scrollView; 25    private LinearLayout pool; 26    private List<LinearLayout> items_layout; //用于存放动态生成的线性布局 27    private AssetManager manager; //assets文件夹的管理器 28    private int screenWidth;  //屏幕的宽度 29    private List<String> namesList; //用于存放所有图片文件的文件名     30    private int currentIndex = 0;; //表示当前页从第几 31      32     @Override 33     protected void onCreate(Bundle savedInstanceState) { 34         super.onCreate(savedInstanceState); 35         setContentView(R.layout.activity_main); 36          37         scrollView = (ScrollView) findViewById(R.id.scrollView); 38         scrollView.setOnTouchListener(this); 39         pool = (LinearLayout) findViewById(R.id.pool); 40          41         manager = getAssets(); 42          43         Display display = getWindowManager().getDefaultDisplay(); 44         screenWidth = display.getWidth(); 45          46         createLayouts(); 47          48         getPicNameList(); 49          loadImage(currentIndex); 50     51     } 52      53     /** 54      *  动态生成三个垂直的线性布局 55      */ 56     public void createLayouts(){ 57         items_layout = new ArrayList<LinearLayout>(); 58         for(int i = 0; i < 3; i++){ 59             LinearLayout item_layout = new LinearLayout(this); 60             item_layout.setOrientation(LinearLayout.VERTICAL); 61             LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(screenWidth/3,android.view.ViewGroup.LayoutParams.WRAP_CONTENT); 62             item_layout.setLayoutParams(params); 63             //将该线性布局添加到pool中 64             pool.addView(item_layout); 65             //将该线性布局添加到集合中 66             items_layout.add(item_layout); 67         } 68          69     } 70      71     /** 72      *   //将assets文件夹下的图片名存到集合中 73      */ 74     public void getPicNameList(){ 75          76         namesList = new ArrayList<String>(); 77         try { 78             //获取到images文件夹下所有图片的文件名数组 79             String[] names = manager.list("images"); 80             //将字符串数据转换为集合 81             namesList.addAll(Arrays.asList(names)); 82         } catch (IOException e) { 83             e.printStackTrace(); 84         } 85          86     } 87     /** 88      *  从指定索引位置处加载图片 89      * @param currentIndex 90      */ 91     public void loadImage(int index ){ 92          93         //用于一次加载的图片的文件名，一次加载9张 94         String[] paths = new String[9]; 95         for(int i = index ,j = 0; i < index +9;i++,j++){ 96             if(i >= namesList.size()){ 97                 break; 98             } 99             paths[j] = namesList.get(i);100             101         }102         103        //获取到图片路径后，就开始加载图片104         int count = 0; //用于计算加载的paths中的第几张图片105         for(String fileName : paths){106             try {107                 //获得bitmap对象108                 InputStream is = manager.open("images/"+fileName);109                 Bitmap bitmap = BitmapFactory.decodeStream(is);110                 111                 //动态创建ImageView112                 ImageView image = new ImageView(this);113                 //设置image的初始尺寸114                 LinearLayout.LayoutParams params1 = new LinearLayout.LayoutParams(screenWidth/3,LinearLayout.LayoutParams.WRAP_CONTENT);115                 image.setLayoutParams(params1);116                 //为image设置默认图片117                 image.setImageResource(R.drawable.ic_launcher);118                 119                 //根据bitmap的大小，重新设置image的高度120                 LayoutParams params2 =   (LayoutParams) image.getLayoutParams();121                 params2.height = params2.width * bitmap.getHeight()/bitmap.getWidth();122                 image.setLayoutParams(params2);123                 image.setImageBitmap(bitmap);124                 125                 //将image添加到垂直线性布局中126                   items_layout.get(count%3).addView(image);127                   count++;128                 129             } catch (IOException e) {130                 e.printStackTrace();131             }132         }133     }134     135     /**136      *  为scrollView添加触摸事件137      */138     @Override139     public boolean onTouch(View view , MotionEvent event) {140     141         int action = event.getAction();142         if(action == MotionEvent.ACTION_UP){ //手指离开屏幕时加载图片143             144             int sy = scrollView.getScrollY(); //滑出scrollView上边界的部分的高度145             int sh = scrollView.getHeight();  //scrollView的高度146             147             int ph = pool.getHeight(); //得到pool的高度148              149             if(sy + sh >= ph){150                 currentIndex += 9;151                 152                 /** 153                  *   方式一：154                  *   155                  * 重复加载所有的图片，过多时，会发生OOM异常156                  * *//*157                 if(currentIndex >= namesList.size()){158                     currentIndex = 0;159                 }160                 loadImage(currentIndex);*/161                 162                 163                 /**164                  *  方式二： 165                  *   将所有的图片只加载一次166                  */167                 if(currentIndex < namesList.size()){168                     loadImage(currentIndex);169                 }170             }171             172         }173         return false;174     }175 176 }