In this section, we will develop an infographic food details page, by building custom components through the container components **\<Stack>** and **\<Flex>** as well as basic components **\<Image>** and **\<Text>**.
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@@ -9,7 +8,7 @@ In this section, we will develop an infographic food details page, by building c
1. Create a food name.
Delete the code of the **build** method in the project template, create a **\<Stack>** component, and place the **\<Text>** component in the braces of the **\<Stack>** component. When the **\<Stack>** component contains multiple child components, the latter child component overwrites the former one.
```
@Entry
@Component
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@@ -21,14 +20,14 @@ In this section, we will develop an infographic food details page, by building c
Create an **\<Image>** component and specify a URL for it. The **\<Image>** and **\<Text>** components are mandatory. To display the **\<Text>** component above the **\<Image>** component, you need to declare the **\<Image>** component first. Image resources are stored in the **rawfile** folder in **resources**. When referencing the resources in the **rawfile** folder, use the `"$rawfile('filename')"` format, where **filename** indicates the relative path of the file in the **rawfile** folder. Currently, `$rawfile` only allows the **\<Image>** component to reference image resources.
Create an **\<Image>** component and specify a URL for it. To display the **\<Text>** component above the **\<Image>** component, declare the **\<Image>** component first. Image resources are stored in the **rawfile** folder in **resources**. When referencing the resources in the **rawfile** folder, use the `$rawfile('filename')` format, where **filename** indicates the relative path of the file in the **rawfile** folder. Currently,` $rawfile` only allows the **\<Image>** component to reference image resources.
```
@Entry
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@@ -45,17 +44,17 @@ In this section, we will develop an infographic food details page, by building c
In addition to specifying the image path, you can also use the media resource symbol `$r` to reference resources in the **resources** folder based on the resource qualifier rules. Right-click the **resources** folder, choose **New**>**Resource Directory**, and set **Resource Type** to **Media (image resource)**.
Place **Tomato.png** in the **media** folder. You can then can reference the application resource in the `$r('app.type.name')` format, that is, `$r('app.media.Tomato')`.
In addition to specifying the image path, you can also use the media resource symbol **$r** to reference resources based on the resource qualifier rules in the **resources** folder. Right-click the **resources** folder, choose **New** > **Resource Directory** from the shortcut menu, and set **Resource Type** to **Media** (image resource).
Place **Tomato.png** in the **media** folder. You can then reference the application resources in the `$r('app.type.name')` format, which is `$r('app.media.Tomato')` in this example.
```
@Entry
```
@Entry
@Component
struct MyComponent {
build() {
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@@ -69,15 +68,18 @@ In this section, we will develop an infographic food details page, by building c
}
}
}
```
```
4. Set the width and height of the image, and set the **objectFit** attribute of the image to **ImageFit.Contain**, which means to keep the aspect ratio of the image to ensure that the image is completely displayed within the boundary. If the image fills the entire screen, the possible causes are as follows:
4. Set the width and height of the image, and set the **objectFit** attribute of the image to **ImageFit.Contain**, which means to keep the aspect ratio of the image to ensure that the image is completely displayed within the boundary.
1. The width and height of the image are not set.
2. The default attribute of **objectFit** of the image is **ImageFit.Cover**, that is, the image is zoomed in or zoomed out to fill the entire display boundary with the aspect ratio locked.
```
@Entry
If the image fills the entire screen, the possible causes are as follows:
- The width and height of the image are not set.
- The default attribute of **objectFit** of the image is **ImageFit.Cover**, that is, the image is zoomed in or zoomed out to fill the entire display boundary with the aspect ratio locked.
```
@Entry
@Component
struct MyComponent {
build() {
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@@ -91,14 +93,17 @@ In this section, we will develop an infographic food details page, by building c
5. Set the food image and name layout. Set **alignContent** to **Alignment.BottomStart**. Similar to **FontWeight**, **Alignment** is a built-in enumeration type provided by the framework.
Set **alignContent** of the **\<Stack>** component to **Alignment.BottomStart**. Similar to **FontWeight**, **Alignment** is a built-in enumeration type provided by the framework.
```
@Entry
@Entry
@Component
struct MyComponent {
build() {
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@@ -114,15 +119,19 @@ In this section, we will develop an infographic food details page, by building c
6. You can change the background color of the food image by setting the background color of the **\<Stack>** component in either of the following ways:
1. Using the built-in **Color** enums provided by the framework. For example, **backgroundColor(Color.Red)** indicates that the background color is set to red.
2. Using the string-type parameter. The supported color formats are rgb, rgba, and HEX. For example, you can set the background color to blue by setting **backgroundColor(??\#0000FF??)** and set the background color to white by setting **backgroundColor(??rgb(255, 255, 255)??)**.
6. You can change the background color of the food image by setting the background color of the **\<Stack>** component in any of the following ways:
1. Using a built-in enumeration value of **Color** provided by the framework. For example, **backgroundColor(Color.Red)** indicates that the background color is set to red.
2. Using a value of the string type. The supported color formats are rgb, rgba, and HEX. For example, you can set the background color to blue through **backgroundColor(??#0000FF??)** and set the background color to white through **backgroundColor(??rgb(255, 255, 255)??)**.
3. Using a value of the number type. Hexadecimal color values are supported. For example, **backgroundColor(0xFF0000)** indicates that the background color is red.
4. Using a value of the Resource type. For details about the Resource type, see [Resource Access](ts-resource-access.md).
```
@Entry
```
@Entry
@Component
struct MyComponent {
build() {
...
...
@@ -136,18 +145,19 @@ In this section, we will develop an infographic food details page, by building c
7. Adjust the left and bottom margin of the **\<Text>** component. **Margin** is a shorthand attribute. You can specify the margins of the four edges in a unified manner or separately. The configuration method is as follows:
1. To set the margins of the four edges in a unified manner, use the **Margin(Length)** format. For example, **margin(20)** indicates that the outer margins of the top, right, bottom, and left edges are all 20.
2. To set the margins of the four edges separately, use the **{top?: Length, right?: Length, bottom?: Length, left?:Length}** format. For example, **margin({ left: 26, bottom: 17.4 })** indicates that the left margin is 26 and the bottom margin is 17.4.
7. Adjust the left and bottom margin of the **\<Text>** component. Margin is a shorthand attribute. You can specify the margins of the four edges in a unified manner or separately.
- To set the margins of the four edges in a unified manner, use the **Margin(Length)** format. For example, **margin(20)** indicates that the margins of the top, right, bottom, and left edges are all 20.
- To set the margins of the four edges separately, use the **{top?: Length, right?: Length, bottom?: Length, left?:Length}** format. For example, **margin({ left: 26, bottom: 17.4 })** indicates that the left margin is 26 and the bottom margin is 17.4.
```
@Entry
```
@Entry
@Component
struct MyComponent {
build() {
...
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@@ -163,17 +173,17 @@ In this section, we will develop an infographic food details page, by building c
8. Adjust the structure between components and semanticize component names. Create the **FoodDetail** page entry component, create a column in **FoodDetail**, and set the alignment to **alignItems(HorizontalAlign.Center)**. Change the name of the **MyComponent** component to **FoodImageDisplay**, which is a child component of the **FoodDetail** component.
A column is a container component whose child components are vertically arranged. It is a linear layout in essence. Therefore, only the alignment in the cross axis direction can be set.
8. Adjust the structure between components and semanticize component names. Create the **FoodDetail** page entry component, create a **\<Column>** component in **FoodDetail**, and set the alignment to **alignItems(HorizontalAlign.Center)**. Change the name of the **MyComponent** component to **FoodImageDisplay**, which is a child component of the **FoodDetail** component.
The **\<Column>** component is a container whose child components are vertically arranged. It is in linear layout in essence. Therefore, only the alignment in the cross axis direction can be set.
```
@Component
```
@Component
struct FoodImageDisplay {
build() {
Stack({ alignContent: Alignment.BottomStart }) {
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@@ -199,17 +209,18 @@ In this section, we will develop an infographic food details page, by building c
.alignItems(HorizontalAlign.Center)
}
}
```
```
## Building the Flex Layout
You can use the Flex layout to build a food composition table. In this way you do not need to worry about the width and height calculation. The size of different cells can be flexibly set based on the proportion.
Use the **Flex** layout to build a food composition table. In this way, cell sizes are flexibly set based on the proportion, eliminating the need for width and height calculation.
1. Create a **ContentTable** component as a child component of the **FoodDetail** component.
```
@Component
```
@Component
struct FoodImageDisplay {
build() {
Stack({ alignContent: Alignment.BottomStart }) {
...
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@@ -241,19 +252,19 @@ You can use the Flex layout to build a food composition table. In this way you d
.alignItems(HorizontalAlign.Center)
}
}
```
```
2. Create a Flex component to display two food composition categories in the tomato: **Calories** and **Nutrition**.
2. Create a **\<Flex>** component to display two food composition categories in the tomato: **Calories** and **Nutrition**.
**Calories** contains information about calories. **Nutrition** contains information about protein, fat, carbohydrates, and vitamin C.
Create the **Calories** class. Create a Flex component and set its height to 280, and the top, right, and left margins to 30. The Flex component contains three **\<Text>** child components, which represent the category name (**Calories**), content name (**Calories**), and contain value (**17 kcal**), respectively. By default, child components in the Flex component are arranged horizontally.
Create the **Calories** class. Create a **\<Flex>** component and set its height to **280**, and the top, right, and left margins to **30**. The **Flex** component contains three **\<Text>** child components, which represent the category name (**Calories**), content name (**Calories**), and contain value (**17 kcal**), respectively. By default, child components in the **Flex** component are arranged horizontally.
In the following example, code of **FoodImageDisplay** is omitted, and only code of **ContentTable** is provided.
```
@Component
```
@Component
struct ContentTable {
build() {
Flex() {
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...
@@ -281,14 +292,15 @@ You can use the Flex layout to build a food composition table. In this way you d
3. Adjust the layout and set the proportion (**layoutWeight**) of each part. Set the proportion of the category name to **1**, and the total proportion of content name and content value to **2**. The content name and content value are in a same Flex, and the content name occupies all remaining space **flexGrow(1)**.
3. Adjust the layout and set the proportion (**layoutWeight**) of each part. Set **layoutWeight** of the category name to **1**, and **layoutWeight** of the content name and content value to **2**. The content name and content value are in a same **Flex**, and the content name occupies all remaining space **flexGrow(1)**.
```
@Component
```
@Component
struct FoodImageDisplay {
build() {
Stack({ alignContent: Alignment.BottomStart }) {
...
...
@@ -337,7 +349,8 @@ You can use the Flex layout to build a food composition table. In this way you d
@@ -438,19 +450,19 @@ You can use the Flex layout to build a food composition table. In this way you d
.alignItems(HorizontalAlign.Center)
}
}
```
```
5. Use the custom constructor @Builder to simplify the code. It can be found that the food groups in each food composition table are actually of the same UI structure.
5. Use the custom constructor **\@Builder** to simplify the code. It can be found that the food groups in each food composition table are actually of the same UI structure.
Currently, all food groups are declared, resulting in code duplication and redundancy. You can use **\@Builder** to build a custom method and abstract the same UI structure declaration. The **\@Builder** decorated method and the **build** method for the **@Component** decorated component are used to declare some UI rendering structures and comply with the same ArkTS syntax. You can define one or more methods decorated by **\@Builder**, but a component decorated by **@Component** can have only one **build** method.
Declare the **IngredientItem** method decorated by **\@Builder** in **ContentTable** to declare the UI descriptions for the category name, content name, and content value.
Currently, all food groups are declared, resulting in code duplication and redundancy. You can use @Builder to build a custom method and abstract the same UI structure declaration. The @Builder decorated method and the build method for the @Component decorated component are used to declare some UI rendering structures and comply with the same eTS syntax. You can define one or more methods decorated by @Builder, but a component decorated by @Component can have only one build method.
Declare the **IngredientItem** method decorated by @Builder in **ContentTable** to declare the UI descriptions for the category name, content name, and content value.
@@ -469,13 +481,13 @@ You can use the Flex layout to build a food composition table. In this way you d
}
}
}
```
```
When the `IngredientItem` API is called in the **build** method of **ContentTable**, `this` needs to be used to invoke the method in the scope of the component to distinguish the global method call.
When the **IngredientItem** API is called in the **build** method of **ContentTable**, **this** needs to be used to invoke the method in the scope of the component to distinguish the global method call.
```
@Component
```
@Component
struct ContentTable {
......
build() {
...
...
@@ -490,13 +502,13 @@ You can use the Flex layout to build a food composition table. In this way you d
.padding({ top: 30, right: 30, left: 30 })
}
}
```
```
The overall code of the **ContentTable** component is as follows:
The overall code of the **ContentTable** component is as follows:
