瀑布流布局结构：
ScrollView * ------------------------------------------------------------ * | LinearLayout (horizontal) | * | -------------------------------------------------------- | * | | LinearLayout LinearLayout LinearLayout | | * | | ---------------- --------------- --------------- | | * | | | | | | | | | | * | | | | | | | | | | * | | | | | | | | | | * | | | Column1 | | Column2 | | Column3 | | | * | | | Vertical | | Vertical | | Vertical | | | * | | | | | | | | | | * | | | | | | | | | | * | | ---------------- --------------- --------------- | | * | -------------------------------------------------------- | * ------------------------------------------------------------
布局文件代码如下：
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/scrollView"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/pool"
android:orientation="horizontal"
>
</LinearLayout>
</ScrollView>
功能实现代码如下：
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ImageView
112 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 @Override
139 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 }
时间： 2024-08-02 13:26:00