1# Development Guidelines on Container Components<a name="EN-US_TOPIC_0000001052810390"></a> 2 3- [UIViewGroup](#section145471898812) 4- [When to Use](#section0916112362216) 5- [Available APIs](#section12641756192212) 6- [How to Develop](#section5412161692311) 7- [UIScrollView](#section174961523161315) 8- [When to Use](#section8937101902413) 9- [Available APIs](#section14789133142420) 10- [How to Develop](#section1769754422417) 11 12Container components are capable of containing UI components and inherit from **UIViewGroup**. Components that are commonly used and need to contain child components are placed in the container class inheritance structure. For example, you need to call the **Add** function to add information such as time statistics and icons to **UIAnalogClock**. 13 14**Figure 1** Structure of common container components<a name="fig1931013319293"></a> 15 16 17The **RootView**, **UIAbstractScroll**, and **UIPicker** components inherit from **UIViewGroup**, and the **UIList**, **UIScrollView**, and **UISwipeView** components inherit from **UIAbstractScroll**. 18 19## UIViewGroup<a name="section145471898812"></a> 20 21## When to Use<a name="section0916112362216"></a> 22 23**UIViewGroup** is a base class for container components. For example, you can call the functions in this class to add, remove, and insert container components. Also, you can call the **Add** function to add child components for a container component. You need to set the position information for child components in a common container component. The position information is the coordinates relative to those of their parent component. The following figure shows the tree structure of components. 24 25**Figure 2** Component tree structure<a name="fig279970183012"></a> 26 27 28As shown in the figure, the container component **ViewGroup1** and the component **View1** are added to **RootView**, the component **View2** and the container component **ViewGroup2** are added to **ViewGroup1**, and then the component **View3** \(as a sibling of **View1**\) is also added to **ViewGroup1**. 29 30- Rendering: During rendering of a container component, you need to call the **OnDraw** function on all its child components to update them. 31- Coordinates: As the position information of child components is the coordinates relative to those of their parent components, the system calculates and displays the absolute coordinates of child components during rendering. 32- Tree structure traversing: The **UIViewGroup** class provides the functions below to traverse, search for, and manage the component tree. 33 34## Available APIs<a name="section12641756192212"></a> 35 36**Table 1** Available functions in ViewGroup 37 38<a name="table15959122392211"></a> 39<table><thead align="left"><tr id="row14957132342220"><th class="cellrowborder" valign="top" width="64.73%" id="mcps1.2.3.1.1"><p id="p3957182302217"><a name="p3957182302217"></a><a name="p3957182302217"></a>Function</p> 40</th> 41<th class="cellrowborder" valign="top" width="35.27%" id="mcps1.2.3.1.2"><p id="p1595742312219"><a name="p1595742312219"></a><a name="p1595742312219"></a>Description</p> 42</th> 43</tr> 44</thead> 45<tbody><tr id="row14957123162218"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p89572023102216"><a name="p89572023102216"></a><a name="p89572023102216"></a>virtual void Add(UIView* view)</p> 46</td> 47<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p1495720236223"><a name="p1495720236223"></a><a name="p1495720236223"></a>Adds a child component.</p> 48</td> 49</tr> 50<tr id="row895892310224"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p16958192315227"><a name="p16958192315227"></a><a name="p16958192315227"></a>virtual void Insert(UIView* prevView, UIView* insertView)</p> 51</td> 52<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p1958223152210"><a name="p1958223152210"></a><a name="p1958223152210"></a>Inserts a child component.</p> 53</td> 54</tr> 55<tr id="row395862315229"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p16958142314223"><a name="p16958142314223"></a><a name="p16958142314223"></a>virtual void Remove(UIView* view)</p> 56</td> 57<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p2095862319224"><a name="p2095862319224"></a><a name="p2095862319224"></a>Removes a child component.</p> 58</td> 59</tr> 60<tr id="row195832352212"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p3958152362219"><a name="p3958152362219"></a><a name="p3958152362219"></a>virtual void RemoveAll()</p> 61</td> 62<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p10958132318225"><a name="p10958132318225"></a><a name="p10958132318225"></a>Removes all child components.</p> 63</td> 64</tr> 65<tr id="row895818232223"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p9958202322214"><a name="p9958202322214"></a><a name="p9958202322214"></a>virtual void GetTargetView(const Point& point, UIView** last)</p> 66</td> 67<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p79584234227"><a name="p79584234227"></a><a name="p79584234227"></a>Obtains the target view.</p> 68</td> 69</tr> 70<tr id="row795917235227"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p5958162362213"><a name="p5958162362213"></a><a name="p5958162362213"></a>virtual void MoveChildByOffset(int16_t x, int16_t y)</p> 71</td> 72<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p18958142315225"><a name="p18958142315225"></a><a name="p18958142315225"></a>Moves a child component by a specified offset.</p> 73</td> 74</tr> 75<tr id="row1395912314227"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p209591223172217"><a name="p209591223172217"></a><a name="p209591223172217"></a>UIView* GetChildrenHead() const</p> 76</td> 77<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p895942313224"><a name="p895942313224"></a><a name="p895942313224"></a>Obtains the first child view in a view group.</p> 78</td> 79</tr> 80<tr id="row7959192317226"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p89591423122213"><a name="p89591423122213"></a><a name="p89591423122213"></a>UIView* GetChildrenTail() const</p> 81</td> 82<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p17959132382217"><a name="p17959132382217"></a><a name="p17959132382217"></a>Obtains the last child view in a view group.</p> 83</td> 84</tr> 85<tr id="row39591423142214"><td class="cellrowborder" valign="top" width="64.73%" headers="mcps1.2.3.1.1 "><p id="p6959623182212"><a name="p6959623182212"></a><a name="p6959623182212"></a>virtual UIView* GetChildById(const char* id) const override</p> 86</td> 87<td class="cellrowborder" valign="top" width="35.27%" headers="mcps1.2.3.1.2 "><p id="p095932319222"><a name="p095932319222"></a><a name="p095932319222"></a>Obtains a child view based on its ID.</p> 88</td> 89</tr> 90</tbody> 91</table> 92 93## How to Develop<a name="section5412161692311"></a> 94 951. Create **ULLabelButton** instances and set their coordinates. 96 97 ``` 98 UILabelButton* btn1 = new UILabelButton(); 99 btn1->SetPosition(0, 0, 100, 50); 100 btn1->SetText("btn1"); 101 102 UILabelButton* btn2 = new UILabelButton(); 103 btn2->SetPosition(50, 50, 100, 50); 104 btn2->SetText("btn2"); 105 106 UILabelButton* btn3 = new UILabelButton(); 107 btn3->SetPosition(100, 100, 100, 50); 108 btn3->SetText("btn3"); 109 ``` 110 1112. Create a **UIViewGroup** instance and set its coordinates. 112 113 ``` 114 UIViewGroup* group = new UIViewGroup(); 115 group->SetPosition(0, 0, 300, 300); 116 ``` 117 1183. Add the **ULLabelButton** instances to **UIViewGroup**. 119 120 ``` 121 group->Add(btn1); 122 group->Add(btn2); 123 group->Add(btn3); 124 ``` 125 1264. The following figure shows the effect of adding view instances to a **ViewGroup**. 127 128 **Figure 3** Effect of adding view instances to a ViewGroup<a name="fig33041856184219"></a> 129  130 131 132## UIScrollView<a name="section174961523161315"></a> 133 134## When to Use<a name="section8937101902413"></a> 135 136**UIScrollView** provides scrolling container components, which enable child components to scroll upwards, downwards, leftwards, and rightwards upon a touch event. This class also supports horizontal and vertical cursor display. 137 138## Available APIs<a name="section14789133142420"></a> 139 140**Table 2** Available functions in ScrollView 141 142<a name="table73572052411"></a> 143<table><thead align="left"><tr id="row432202014249"><th class="cellrowborder" valign="top" width="50%" id="mcps1.2.3.1.1"><p id="p432142092415"><a name="p432142092415"></a><a name="p432142092415"></a>Function</p> 144</th> 145<th class="cellrowborder" valign="top" width="50%" id="mcps1.2.3.1.2"><p id="p4323208245"><a name="p4323208245"></a><a name="p4323208245"></a>Description</p> 146</th> 147</tr> 148</thead> 149<tbody><tr id="row13392032417"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p632182022417"><a name="p632182022417"></a><a name="p632182022417"></a>void ScrollBy(int16_t xDistance, int16_t yDistance)</p> 150</td> 151<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p13333208242"><a name="p13333208242"></a><a name="p13333208242"></a>Scrolls a view.</p> 152</td> 153</tr> 154<tr id="row1633132032415"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p1533320172413"><a name="p1533320172413"></a><a name="p1533320172413"></a>void SetScrollbarWidth(uint8_t width)</p> 155</td> 156<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p173322015241"><a name="p173322015241"></a><a name="p173322015241"></a>Sets the scrollbar width.</p> 157</td> 158</tr> 159<tr id="row033152012416"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p173382042417"><a name="p173382042417"></a><a name="p173382042417"></a>void SetHorizontalScrollState(bool state)</p> 160</td> 161<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p103362042411"><a name="p103362042411"></a><a name="p103362042411"></a>Sets the horizontal scrolling state.</p> 162</td> 163</tr> 164<tr id="row03362011242"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p333152032413"><a name="p333152032413"></a><a name="p333152032413"></a>bool GetHorizontalScrollState() const</p> 165</td> 166<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p9331220192418"><a name="p9331220192418"></a><a name="p9331220192418"></a>Checks whether horizontal scrolling is allowed.</p> 167</td> 168</tr> 169<tr id="row1933520142413"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p1833520192410"><a name="p1833520192410"></a><a name="p1833520192410"></a>void SetVerticalScrollState(bool state)</p> 170</td> 171<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p12331520132415"><a name="p12331520132415"></a><a name="p12331520132415"></a>Sets the vertical scrolling state.</p> 172</td> 173</tr> 174<tr id="row183318200243"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p63317207248"><a name="p63317207248"></a><a name="p63317207248"></a>bool GetVerticalScrollState() const</p> 175</td> 176<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p1133020112417"><a name="p1133020112417"></a><a name="p1133020112417"></a>Checks whether vertical scrolling is allowed.</p> 177</td> 178</tr> 179<tr id="row43462072418"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p193313203245"><a name="p193313203245"></a><a name="p193313203245"></a>void SetXScrollBarVisible(bool state)</p> 180</td> 181<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p1833102017242"><a name="p1833102017242"></a><a name="p1833102017242"></a>Sets whether the x-axis scrollbar is visible.</p> 182</td> 183</tr> 184<tr id="row1834720132417"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p8341620162410"><a name="p8341620162410"></a><a name="p8341620162410"></a>void SetYScrollBarVisible(bool state)</p> 185</td> 186<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p163462092412"><a name="p163462092412"></a><a name="p163462092412"></a>Sets whether the y-axis scrollbar is visible.</p> 187</td> 188</tr> 189<tr id="row13482082411"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p33415208244"><a name="p33415208244"></a><a name="p33415208244"></a>void RegisterScrollListener(OnScrollListener* scrollListener)</p> 190</td> 191<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p934112002417"><a name="p934112002417"></a><a name="p934112002417"></a>Registers the scrolling callback class.</p> 192</td> 193</tr> 194<tr id="row934192014242"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p18341020132410"><a name="p18341020132410"></a><a name="p18341020132410"></a>void RefreshScrollBar()</p> 195</td> 196<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p234520192417"><a name="p234520192417"></a><a name="p234520192417"></a>Refreshes the scrollbar.</p> 197</td> 198</tr> 199<tr id="row63422072418"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p8341620172411"><a name="p8341620172411"></a><a name="p8341620172411"></a>virtual void OnScrollStart() {}</p> 200</td> 201<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p193452052417"><a name="p193452052417"></a><a name="p193452052417"></a>Called when scrolling starts.</p> 202</td> 203</tr> 204<tr id="row93432017244"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p143416203242"><a name="p143416203242"></a><a name="p143416203242"></a>virtual void OnScrollEnd() {}</p> 205</td> 206<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p534152018243"><a name="p534152018243"></a><a name="p534152018243"></a>Called when scrolling ends.</p> 207</td> 208</tr> 209<tr id="row33532012247"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p1834172052419"><a name="p1834172052419"></a><a name="p1834172052419"></a>uint8_t GetScrollState() const</p> 210</td> 211<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p1346205242"><a name="p1346205242"></a><a name="p1346205242"></a>Obtains the scrolling state.</p> 212</td> 213</tr> 214<tr id="row1535142022415"><td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.1 "><p id="p173532082413"><a name="p173532082413"></a><a name="p173532082413"></a>void SetScrollState(uint8_t state)</p> 215</td> 216<td class="cellrowborder" valign="top" width="50%" headers="mcps1.2.3.1.2 "><p id="p1235102016242"><a name="p1235102016242"></a><a name="p1235102016242"></a>Sets the scrolling state.</p> 217</td> 218</tr> 219</tbody> 220</table> 221 222## How to Develop<a name="section1769754422417"></a> 223 224Add two buttons as child components and display horizontal and vertical cursors. 225 226``` 227scrollView* scroll = new UIScrollView(); 228scroll->SetStyle(STYLE_BACKGROUND_COLOR, Color::Red().full); 229scroll->SetPosition(0,0, 200, 200); 230scroll->SetXScrollBarVisible(true); 231scroll->SetYScrollBarVisible(true); 232UILabelButton* button1 = new UILabelButton(); 233button1->SetText("button1"); 234button1->SetPosition(0, 0, 300, 300); 235UILabelButton* button2 = new UILabelButton(); 236button2->SetText("button2"); 237button2->SetPosition(0, 300, 300, 300); 238scroll->Add(button1); 239scroll->Add(button2); 240``` 241 242**Figure 4** Scrolling effect in both horizontal and vertical directions<a name="fig99017432114"></a> 243 244 245
