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网站建设和网站,iis 建设网站,网站建设前期预算,创意网站建设价格多少JetpackCompose从入门到实战学习笔记8—ConstraintLayout的简单使用 1.简介#xff1a; Compose 中的 ConstraintLayout ConstraintLayout 是一种布局#xff0c;让您可以相对于屏幕上的其他可组合项来放置可组合项。它是一种实用的替代方案#xff0c;可代替使用多个已嵌…JetpackCompose从入门到实战学习笔记8—ConstraintLayout的简单使用 1.简介 Compose 中的 ConstraintLayout ConstraintLayout 是一种布局让您可以相对于屏幕上的其他可组合项来放置可组合项。它是一种实用的替代方案可代替使用多个已嵌套的 Row、Column、Box 和其他自定义布局元素这种做法。在实现对齐要求比较复杂的较大布局时ConstraintLayout 很有用。 在以下情况下考虑使用 ConstraintLayout 为了避免在屏幕上定位元素时嵌套多个 Column 和 Row以便提高代码的可读性。相对于其它可组合项来定位可组合项或根据引导线、屏障线或链来定位可组合项。 在 View 系统中建议使用 ConstraintLayout 来创建复杂的大型布局因为扁平视图层次结构比嵌套视图的效果更好。不过这在 Compose 中不是什么问题因为 Compose 能够高效地处理较深的布局层次结构。 2.在build.gradle中添加依赖 implementation androidx.constraintlayout:constraintlayout-compose:1.0.13.可组合项简单使用 Composable fun ConstraintLayoutContent() {ConstraintLayout {// Create references for the composables to constrainval (button, text) createRefs()Button(onClick { /* Do something / },// Assign reference button to the Button composable// and constrain it to the top of the ConstraintLayoutmodifier Modifier.constrainAs(button) {top.linkTo(parent.top, margin 16.dp)}) {Text(Button)}// Assign reference text to the Text composable// and constrain it to the bottom of the Button composableText(Android, Modifier.constrainAs(text) {top.linkTo(button.bottom, margin 16.dp)})} }4.效果如下 5.Barrier分界线: PreviewComposablefun InputFieldLayoutDemo() {ConstraintLayout(modifier Modifier.width(400.dp).height(100.dp).padding(10.dp)) {val (usernameTextRef, passwordTextRef, usernameInputRef, passWordInputRef, dividerRef) remember { createRefs() }var barrier createEndBarrier(usernameTextRef, passwordTextRef)Text(text 用户名,fontSize 14.sp,textAlign TextAlign.Left,modifier Modifier.constrainAs(usernameTextRef) {top.linkTo(parent.top)start.linkTo(parent.start)})Divider(Modifier.fillMaxWidth().constrainAs(dividerRef) {top.linkTo(usernameTextRef.bottom)bottom.linkTo(passwordTextRef.top)})Text(text 密码,fontSize 14.sp,modifier Modifier.constrainAs(passwordTextRef) {top.linkTo(usernameTextRef.bottom, 19.dp)start.linkTo(parent.start)})OutlinedTextField(value ,onValueChange {},modifier Modifier.constrainAs(usernameInputRef) {start.linkTo(barrier, 10.dp)top.linkTo(usernameTextRef.top)bottom.linkTo(usernameTextRef.bottom)height Dimension.fillToConstraints})OutlinedTextField(value ,onValueChange {},modifier Modifier.constrainAs(passWordInputRef) {start.linkTo(barrier, 10.dp)top.linkTo(passwordTextRef.top)bottom.linkTo(passwordTextRef.bottom)height Dimension.fillToConstraints})}}6.效果如下 7.GuideLine引导线: PreviewComposablefun GuidelineSample(){ConstraintLayout(modifier Modifier.fillMaxSize().padding(10.dp).background(Color.White)) {val topGuideline createGuidelineFromTop(0.2f)var (userPortraitBackgroundRef, userPortraitImgRef, welcomeRef, quotesRef) remember { createRefs() }Box(modifier Modifier.background(Color.Green).constrainAs(userPortraitBackgroundRef) {top.linkTo(parent.top)bottom.linkTo(topGuideline)height Dimension.fillToConstraintswidth Dimension.matchParent})Image(painter painterResource(id R.mipmap.avatar),contentDescription stringResource(R.string.description),contentScale ContentScale.Crop,modifier Modifier.constrainAs(userPortraitImgRef){top.linkTo(topGuideline)bottom.linkTo(topGuideline)start.linkTo(parent.start)end.linkTo(parent.end)}.size(100.dp).clip(CircleShape).border(width 2.dp, color Color.Red, shape CircleShape))Text(text Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose ,fontSize 24.sp,maxLines 1,textAlign TextAlign.Center,overflow TextOverflow.Ellipsis,//1行显示不下时是否显示。。。modifier Modifier.constrainAs(welcomeRef) {top.linkTo(userPortraitImgRef.bottom, 30.dp)start.linkTo(parent.start)end.linkTo(parent.end)width Dimension.preferredWrapContent})}}//这里有个小技巧若要想TextView一行铺满但没有完全显示且显示。。。时设置 overflow TextOverflow.Ellipsis属性8.效果如下 9.Chain链接约束: /** Chain链接约束,Compose提供了ChainStyle* 1.Spread:链条中美国元素均分整个parent空间。* 2.SpreadInside:链条中首尾元素紧贴边界剩下每个元素平分整个parent空间。* 3.Packed:链条在所有元素聚焦到中间。/PreviewComposablefun ChainDemo() {ConstraintLayout(modifier Modifier.fillMaxSize().background(Color.Gray)) {val (quotesFirstLineRef, quotesSecondLineRef, quotesThirdLineRef, quotesForthLineRef) remember { createRefs() }createVerticalChain(quotesFirstLineRef, quotesSecondLineRef, quotesThirdLineRef, quotesForthLineRef,chainStyle ChainStyle.SpreadInside)Text(text 寄蜉蝣于天地,color Color.White,fontSize 30.sp,fontWeight FontWeight.Bold,modifier Modifier.constrainAs(quotesFirstLineRef) {start.linkTo(parent.start)end.linkTo(parent.end)})Text(text 渺沧海之一粟。,color Color.White,fontSize 30.sp,fontWeight FontWeight.Bold,modifier Modifier.constrainAs(quotesSecondLineRef) {start.linkTo(parent.start)end.linkTo(parent.end)})Text(text 哀吾生之须臾,color Color.White,fontSize 30.sp,fontWeight FontWeight.Bold,modifier Modifier.constrainAs(quotesThirdLineRef) {start.linkTo(parent.start)end.linkTo(parent.end)})Text(text 羡长江之无穷。,color Color.White,fontSize 30.sp,fontWeight FontWeight.Bold,modifier Modifier.constrainAs(quotesForthLineRef) {start.linkTo(parent.start)end.linkTo(parent.end)})}}10.Spread模式效果如下 Spread模式:链条中美国元素均分整个parent空间。 11.SpreadInside模式效果如下 SpreadInside:链条中首尾元素紧贴边界剩下每个元素平分整个parent空间。 12.Packed模式效果如下 Packed:链条在所有元素聚焦到中间。 13.完整代码如下 import android.os.Bundle import android.widget.ScrollView import androidx.activity.ComponentActivity import androidx.activity.compose.setContent import androidx.compose.foundation.Image import androidx.compose.foundation.background import androidx.compose.foundation.border import androidx.compose.foundation.layout. import androidx.compose.foundation.shape.CircleShape import androidx.compose.material.* import androidx.compose.runtime.Composable import androidx.compose.runtime.remember import androidx.compose.ui.Modifier import androidx.compose.ui.draw.clip import androidx.compose.ui.graphics.Color import androidx.compose.ui.layout.ContentScale import androidx.compose.ui.res.painterResource import androidx.compose.ui.res.stringResource import androidx.compose.ui.text.font.FontWeight import androidx.compose.ui.text.style.TextAlign import androidx.compose.ui.text.style.TextOverflow import androidx.compose.ui.tooling.preview.Preview import androidx.compose.ui.unit.dp import androidx.compose.ui.unit.sp import androidx.constraintlayout.compose.ChainStyle import androidx.constraintlayout.compose.ConstraintLayout import androidx.constraintlayout.compose.Dimension/*** auth: njb* date: 2023/1/17 16:36* desc:/ class ConstraintLayoutActivity:ComponentActivity() {override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContent {// ConstraintLayoutContent()// ConstraintLayoutSample()//InputFieldLayoutDemo()//GuidelineSample()ChainDemo()}}PreviewComposablefun ConstraintLayoutContent() {ConstraintLayout {// Create references for the composables to constrainval (button, text) createRefs()Button(onClick { / Do something / },// Assign reference button to the Button composable// and constrain it to the top of the ConstraintLayoutmodifier Modifier.constrainAs(button) {top.linkTo(parent.top, margin 16.dp)}) {Text(Button)}// Assign reference text to the Text composable// and constrain it to the bottom of the Button composableText(Android, Modifier.constrainAs(text) {top.linkTo(button.bottom, margin 16.dp)})}}PreviewComposablefun ConstraintLayoutSample(){ConstraintLayout(modifier Modifier.width(400.dp).height(300.dp).padding(10.dp)) {// Create references for the composables to constrainval (button, text) createRefs()Button(onClick { },// Assign reference button to the Button composable// and constrain it to the top of the ConstraintLayoutmodifier Modifier.constrainAs(button) {top.linkTo(parent.top, margin 6.dp)}) {Text(Button)}// Assign reference text to the Text composable// and constrain it to the bottom of the Button composableText(Android, Modifier.constrainAs(text) {top.linkTo(button.bottom, margin 6.dp)})val (portraitImageRef, usernameTextRef, desTextRef) remember { createRefs() }Image(painter painterResource(id R.mipmap.avatar),contentDescription stringResource(R.string.description),contentScale ContentScale.Crop,modifier Modifier.constrainAs(portraitImageRef){top.linkTo(parent.top)bottom.linkTo(parent.bottom)}.size(100.dp))Text(text Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose ,fontSize 14.sp,maxLines 1,textAlign TextAlign.Center,overflow TextOverflow.Ellipsis,//1行显示不下时是否显示。。。modifier Modifier.constrainAs(usernameTextRef) {top.linkTo(portraitImageRef.top)start.linkTo(portraitImageRef.end, 10.dp)end.linkTo(parent.end, 10.dp)width Dimension.preferredWrapContent})Text(text 我的个人描述…,fontSize 14.sp,color Color.Red,fontWeight FontWeight.Light,modifier Modifier.constrainAs(desTextRef) {top.linkTo(usernameTextRef.bottom, 5.dp)start.linkTo(portraitImageRef.end, 10.dp)})}}PreviewComposablefun GuidelineSample(){ConstraintLayout(modifier Modifier.fillMaxSize().padding(10.dp).background(Color.White)) {val topGuideline createGuidelineFromTop(0.2f)var (userPortraitBackgroundRef, userPortraitImgRef, welcomeRef, quotesRef) remember { createRefs() }Box(modifier Modifier.background(Color.Green).constrainAs(userPortraitBackgroundRef) {top.linkTo(parent.top)bottom.linkTo(topGuideline)height Dimension.fillToConstraintswidth Dimension.matchParent})Image(painter painterResource(id R.mipmap.avatar),contentDescription stringResource(R.string.description),contentScale ContentScale.Crop,modifier Modifier.constrainAs(userPortraitImgRef){top.linkTo(topGuideline)bottom.linkTo(topGuideline)start.linkTo(parent.start)end.linkTo(parent.end)}.size(100.dp).clip(CircleShape).border(width 2.dp, color Color.Red, shape CircleShape))Text(text Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose 技术爱好者Compose ,fontSize 24.sp,maxLines 1,textAlign TextAlign.Center,overflow TextOverflow.Ellipsis,//1行显示不下时是否显示。。。modifier Modifier.constrainAs(welcomeRef) {top.linkTo(userPortraitImgRef.bottom, 30.dp)start.linkTo(parent.start)end.linkTo(parent.end)width Dimension.preferredWrapContent})}}PreviewComposablefun InputFieldLayoutDemo() {ConstraintLayout(modifier Modifier.width(400.dp).height(100.dp).padding(10.dp)) {val (usernameTextRef, passwordTextRef, usernameInputRef, passWordInputRef, dividerRef) remember { createRefs() }var barrier createEndBarrier(usernameTextRef, passwordTextRef)Text(text 用户名,fontSize 14.sp,textAlign TextAlign.Left,modifier Modifier.constrainAs(usernameTextRef) {top.linkTo(parent.top)start.linkTo(parent.start)})Divider(Modifier.fillMaxWidth().constrainAs(dividerRef) {top.linkTo(usernameTextRef.bottom)bottom.linkTo(passwordTextRef.top)})Text(text 密码,fontSize 14.sp,modifier Modifier.constrainAs(passwordTextRef) {top.linkTo(usernameTextRef.bottom, 19.dp)start.linkTo(parent.start)})OutlinedTextField(value ,onValueChange {},modifier Modifier.constrainAs(usernameInputRef) {start.linkTo(barrier, 10.dp)top.linkTo(usernameTextRef.top)bottom.linkTo(usernameTextRef.bottom)height Dimension.fillToConstraints})OutlinedTextField(value ,onValueChange {},modifier Modifier.constrainAs(passWordInputRef) {start.linkTo(barrier, 10.dp)top.linkTo(passwordTextRef.top)bottom.linkTo(passwordTextRef.bottom)height Dimension.fillToConstraints})}}/** Chain链接约束,Compose提供了ChainStyle* 1.Spread:链条中美国元素均分整个parent空间* 2.SpreadInside:* 3.Packed:*/PreviewComposablefun ChainDemo() {ConstraintLayout(modifier Modifier.fillMaxSize().background(Color.Gray)) {val (quotesFirstLineRef, quotesSecondLineRef, quotesThirdLineRef, quotesForthLineRef) remember { createRefs() }createVerticalChain(quotesFirstLineRef, quotesSecondLineRef, quotesThirdLineRef, quotesForthLineRef,chainStyle ChainStyle.Packed)Text(text 寄蜉蝣于天地,color Color.White,fontSize 30.sp,fontWeight FontWeight.Bold,modifier Modifier.constrainAs(quotesFirstLineRef) {start.linkTo(parent.start)end.linkTo(parent.end)})Text(text 渺沧海之一粟。,color Color.White,fontSize 30.sp,fontWeight FontWeight.Bold,modifier Modifier.constrainAs(quotesSecondLineRef) {start.linkTo(parent.start)end.linkTo(parent.end)})Text(text 哀吾生之须臾,color Color.White,fontSize 30.sp,fontWeight FontWeight.Bold,modifier Modifier.constrainAs(quotesThirdLineRef) {start.linkTo(parent.start)end.linkTo(parent.end)})Text(text 羡长江之无穷。,color Color.White,fontSize 30.sp,fontWeight FontWeight.Bold,modifier Modifier.constrainAs(quotesForthLineRef) {start.linkTo(parent.start)end.linkTo(parent.end)})}} }14.完整效果预览如下