创建自定义ViewGroup
?一，概要：
使用自定义View 和ViewGroup组织应用程序布局是一个好方法，定制组件的同时允许开发者提供自定义行为和功能，以后，开发者
在需要创建复杂布局的视乎，首先应该考虑使用自定义ViewGroup是不是更适合，虽然在开始时，这样做会增加一定的工作量，但是，这是值得的
?二，基本知识点：
要想绘制自定义ViewGroup要涉及到两个方法:
measure(int , int)：该方法从上到下遍历视图树。在递归遍历过程中，每个视图都会从下层传递尺寸和规格。当measure方法遍历结束，每个视图都保存了各自的尺寸信息。
layout(int, int, int, int)：该方法也是从上而下遍历视图树，在遍历过程中，每个父视图通过测量过程的结果定位所有子视图的位置信息。
思路整理：
- 要设置每个子View的横向偏移和竖向偏移普通的android属性中没有，所以需要自定义属性来获取值后来进行设置
- 通过复写ViewGroup中的onMeasure(int,int)方法测量Viewgroup和子View的大小，从而利用onLayout(int,int,int,int)来放置到具体区域
三.效果图：
四.代码：
1)自定义属性，在res/values中没有attr.xml文件就新建一个
1 <?xml version="1.0" encoding="utf-8"?> 2 <resources> 3 4 <declare-styleable name="myrectangle"> 5 <attr name="horizontal_distance" format="dimension" /> 6 <attr name="verticle_distance" format="dimension" /> 7 </declare-styleable> 8 <declare-styleable name="MyLayoutParams"> 9 <attr name="layout_verticle_distance" format="dimension" /> 10 </declare-styleable> 11 12 </resources>
2）设置这些属性未指定时的默认值大小，在dimens.xml中添加：
1 <dimen name="myRectangle_horizontal_distance">10dp</dimen> 2 <dimen name="myRectangle_verticle_distance">10dp</dimen>
3）自定义ViewGroup
1 public class MyViewGoup extends ViewGroup {
2
3 private int mHorzntialDistance;
4
5 private int mVerticalDIstance;
6
7 public MyViewGoup(Context context) {
8 super(context);
9 }
10
11 public MyViewGoup(Context context, AttributeSet attrs) {
12 super(context, attrs);
13 /**
14 * 获取自定义属性值
15 */
16 TypedArray a = context.obtainStyledAttributes(attrs,
17 R.styleable.myrectangle);
18 try {
19
20 mHorzntialDistance = a.getDimensionPixelSize(
21 R.styleable.myrectangle_horizontal_distance,
22 getResources().getDimensionPixelSize(
23 R.dimen.myRectangle_horizontal_distance));
24 mVerticalDIstance = a.getDimensionPixelSize(
25 R.styleable.myrectangle_verticle_distance,
26 getResources().getDimensionPixelSize(
27 R.dimen.myRectangle_verticle_distance));
28 } finally {
29 a.recycle();
30 }
31 }
32
33 public MyViewGoup(Context context, AttributeSet attrs, int defStyle) {
34 super(context, attrs, defStyle);
35 }
36
37 @Override
38 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
39 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
40 int width = getPaddingLeft();
41 int height = getPaddingTop();
42 /**
43 * 测量子view的大小
44 */
45 int childrenCount = getChildCount();
46 int verticleDistance;
47 for (int i = 0; i < childrenCount; i++) {
48 View child = getChildAt(i);
49 measureChild(child, widthMeasureSpec, heightMeasureSpec);
50 /**
51 * 子View设置了自定义属性值就lp中verticleDistance就会获取到值
52 */
53 LayoutParams lp = (LayoutParams) child.getLayoutParams();
54 width = getPaddingLeft() + mHorzntialDistance * i;
55 lp.x = width;
56 lp.y = height;
57 verticleDistance = mVerticalDIstance;
58
59 if (lp.verticleDistance > 0) {
60 verticleDistance += lp.verticleDistance;
61 }
62 width += child.getMeasuredWidth();
63 height += verticleDistance;
64 }
65 /**
66 * 给ViewGroup设置大小. /** 因为设计者可以通过调用setMeasuredDimension决定视图的最终大小
67 * ，例如调用setMeasuredDimension
68 * （100，100）将视图的mMeasuredWidth和mMeasuredHeight设置为100
69 * ，100，那么父视图提供的大小以及程序员在xml中设置的layout_width和layout_height将完全不起作用
70 * ，当然良好的设计一般会根据子视图的measureSpec来设置mMeasuredWidth和mMeasuredHeight的大小
71 */
72 width += getPaddingRight();
73 height += getChildAt(getChildCount() - 1).getMeasuredHeight()
74 + getPaddingBottom();
75
76 if (MeasureSpec.getMode(widthMeasureSpec) == MeasureSpec.EXACTLY) {
77 System.out.println("是AT_MOST,AT_MOST,AT_MOSTAT_MOSTAT_MOSTAT_MOST");
78 }
79
80 /**
81 * resolveSize的源码
82 * public static int resolveSize(int size, int measureSpec) {
83 int result = size;
84 int specMode = MeasureSpec.getMode(measureSpec);
85 int specSize = MeasureSpec.getSize(measureSpec);
86 switch (specMode) {
87 case MeasureSpec.UNSPECIFIED:
88 result = size;
89 break;
90 case MeasureSpec.AT_MOST:
91 result = Math.min(size, specSize);
92 break;
93 case MeasureSpec.EXACTLY:
94 result = specSize;
95 break;
96 }
97 return result;
98 }
99 所以不管怎么谁知其实都是屏幕的大小，这widthMeasureSpec的mode类型是EXACTLY
100 */
101 setMeasuredDimension(resolveSize(width, widthMeasureSpec),
102 resolveSize(height, heightMeasureSpec));
103 }
104
105 @Override
106 protected void onLayout(boolean changed, int l, int t, int r, int b) {
107
108 /**
109 * 给子View设置位置(其实感觉是指定一块区域)
110 */
111
112 int childrenCount = getChildCount();
113 for (int i = 0; i < childrenCount; i++) {
114 View child = getChildAt(i);
115 LayoutParams lp = (LayoutParams) child.getLayoutParams();
116 child.layout(lp.x, lp.y, lp.x + child.getMeasuredWidth(), lp.y
117 + child.getMeasuredHeight());
118
119 }
120
121 }
122
123 @Override
124 protected boolean checkLayoutParams(android.view.ViewGroup.LayoutParams p) {
125 return p instanceof LayoutParams;
126 }
127
128 @Override
129 protected LayoutParams generateDefaultLayoutParams() {
130 return new LayoutParams(LayoutParams.WRAP_CONTENT,
131 LayoutParams.WRAP_CONTENT);
132 }
133
134 @Override
135 public LayoutParams generateLayoutParams(AttributeSet attrs) {
136 return new LayoutParams(getContext(), attrs);
137 }
138
139 @Override
140 protected LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
141 return new LayoutParams(p.width, p.height);
142 }
143
144 private class LayoutParams extends ViewGroup.LayoutParams {
145
146 int x;
147 int y;
148 public int verticleDistance;
149
150 public LayoutParams(Context context, AttributeSet attrs) {
151 super(context, attrs);
152
153 TypedArray a = context.obtainStyledAttributes(attrs,
154 R.styleable.MyLayoutParams);
155 try {
156 /**
157 * 获取子View设置的竖直偏移量
158 */
159 verticleDistance = a
160 .getDimensionPixelSize(
161 R.styleable.MyLayoutParams_layout_verticle_distance,
162 -1);
163 } finally {
164 a.recycle();
165 }
166
167 }
168
169 public LayoutParams(int x, int y) {
170 super(x, y);
171 }
172
173 public LayoutParams(android.view.ViewGroup.LayoutParams arg0) {
174 super(arg0);
175 }
176
177 }
178
179 }
4)activity_main.xml
1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 2 xmlns:tools="http://schemas.android.com/tools" 3 xmlns:myrectangle="http://schemas.android.com/apk/res/com.example.myviewgroup" 4 android:layout_width="match_parent" 5 android:layout_height="match_parent" 6 tools:context=".MainActivity" > 7 8 <com.example.myviewgroup.view.MyViewGoup 9 android:layout_width="match_parent" 10 android:layout_height="match_parent" 11 android:background="#FF00FF" 12 myrectangle:horizontal_distance="70dp" 13 myrectangle:verticle_distance="50dp" > 14 15 <View 16 android:layout_width="100dp" 17 android:layout_height="150dp" 18 android:background="#FF0000" /> 19 20 <View 21 android:layout_width="100dp" 22 android:layout_height="150dp" 23 android:background="#00FF00" /> 24 25 <View 26 android:layout_width="100dp" 27 android:layout_height="150dp" 28 android:background="#0000FF" /> 29 </com.example.myviewgroup.view.MyViewGoup> 30 31 </LinearLayout>
时间： 2024-11-08 21:59:23