Android Compose实现联系人列表流程
作者：会编程的猩猩
声明式UI，更简单的自定义，实时带交互的预览功能Compose并不是类似于Recyclerview的高级控件，而是直接抛弃了View，ViewGroup那套东西，从上到下鲁了一套全新的框架，直白点说就是它的渲染机制，布局机制，触摸算法，以及UI具体写法全都是新的
准备数据
data class ContactEntity(
val letter: Char,
val name: String,
val color: Color
)
/**
* 获取联系人数据
*/
fun getContactData(): MutableList<ContactEntity> {
val contactList = mutableListOf<ContactEntity>()
(65..90).forEach { letter ->
// val random = (5..20).random()
val random = 5
repeat(random) { index ->
contactList.add(
ContactEntity(
letter = letter.toChar(), name = "联系人 $index",
color = Color(
red = (0..255).random(),
blue = (0..255).random(),
green = (0..255).random()
)
)
)
}
}
return contactList
}
/**
* 获取首字母列表
*/
fun getCharList(): MutableList<Char> {
val charList = mutableListOf<Char>()
(65..90).forEach { letter ->
charList.add(letter.toChar())
}
return charList
}
思路
- 整体是由Box布局包裹， 左侧是LazyColumn 右侧放置自定义布局
- 左侧LazyColumn用state来观察滑动的一些参数，来控制右侧字母的位置
- 右侧使用canvas绘制字母 在触控的时候使用scrollToItem准确的定位到左侧应该滑动的位置，感觉有些不准确，不知道是计算的问题还是bug，在谷歌上看到类似的issue提交。
- 中间显示滑动到的字母，也可以使用贝塞尔曲线来绘制类似于水滴的样式，懒得去搞了。
- 利用derivedStateOf来跟踪变化的remember数据，这样可以减少性能的损耗，但是感觉有个地方没处理好，就是触摸的时候需要改变，滑动的时候也需要改变，而derivedStateOf是val类型的，不能直接赋值，所以又设置了一个remember变量。有可以优化的地方请指出。
- 数据和样式都可以自定义，非常方便
代码实现
@OptIn(ExperimentalTextApi::class)
@Composable
fun ContactPage(navCtrl: NavHostController, title: String) {
//联系人数据
val contactList = getContactData()
//字母数据
val charList = getCharList()
val offsetY = with(LocalDensity.current) {
20.dp.toPx()
}
val offsetX = with(LocalDensity.current) {
25.dp.toPx()
}
val coroutineScope = rememberCoroutineScope()
val textMeasure = rememberTextMeasurer()
val state = rememberLazyListState()
//触摸的位置
var touchOffset by remember() {
mutableStateOf(Offset.Zero)
}
//触摸到的上一次的字母下标
var touchIndexLast by remember {
mutableStateOf(-1)
}
//触摸的字母的下标
val touchIndex = remember(touchOffset.y) {
derivedStateOf {
if (touchOffset.y > 0f) {
//通过偏移的倍数计算滑动到哪个字母的位置了
val y = (touchOffset.y / offsetY).roundToInt()
if (y in 0..25) {
touchIndexLast = y
y
} else {
touchIndexLast
}
} else touchIndexLast
}
}
//触摸到的字符的index
val touchLetterIndex = remember {
derivedStateOf {
if (state.isScrollInProgress && state.layoutInfo.visibleItemsInfo.isNotEmpty()) {
val key = state.layoutInfo.visibleItemsInfo[0].key
if (key is Int && key < contactList.size) {
val letter = contactList[key].letter
val findIndex = charList.indexOfFirst {
it == letter
}
findIndex
} else {
touchIndex.value
}
} else {
touchIndex.value
}
}
}
//上一次选择的letter
var lastLetter by remember {
mutableStateOf("")
}
//滑动到的letter
val scrollLetter = remember {
derivedStateOf {
if (touchIndex.value > 0) {
val letter = (65 + touchIndex.value).toChar()
coroutineScope.launch {
//找到相应的item
val index = getIndex(contactList, letter)
state.scrollToItem(index, scrollOffset = 20)
}
val str = letter.toString()
lastLetter = str
str
} else {
lastLetter
}
}
}
CommonToolbar(navCtrl, title) {
Box(modifier = Modifier.fillMaxSize()) {
LazyColumn(modifier = Modifier.fillMaxWidth(), state = state, content = {
contactList.forEachIndexed { index, contactEntity ->
item(key = index) {
Column(
modifier = Modifier.fillMaxWidth()
) {
Row(
modifier = Modifier
.fillMaxWidth()
.padding(horizontal = 10.dp),
verticalAlignment = Alignment.CenterVertically
) {
Box(
modifier = Modifier
.size(50.dp)
.clip(CircleShape)
.background(
color = contactEntity.color,
), contentAlignment = Alignment.Center
) {
Text(
text = "${contactEntity.letter}",
fontSize = 16.sp,
color = Color.White,
fontWeight = FontWeight.SemiBold,
)
}
Text(
text = contactEntity.name,
modifier = Modifier
.padding(20.dp)
.weight(1f)
.padding(horizontal = 10.dp, vertical = 16.dp)
)
}
Divider()
}
}
}
item {
Text(
text = "共${contactList.size}联系人",
fontSize = 12.sp,
color = Color(0xFF333333),
modifier = Modifier
.fillMaxWidth()
.padding(vertical = 20.dp),
textAlign = TextAlign.Center
)
}
})
//绘制右侧的26个字母
Canvas(modifier = Modifier
.padding(top = 30.dp)
.width(50.dp)
.fillMaxHeight()
.align(Alignment.TopEnd)
.pointerInput(Unit) {
coroutineScope {
while (true) {
// down事件
val downPointerInputChange = awaitPointerEventScope {
awaitFirstDown()
}
// 如果位置不在手指按下的位置，先动画的形式过度到手指按下的位置
if (touchOffset.x != downPointerInputChange.position.x && touchOffset.y != downPointerInputChange.position.y) {
launch {
touchOffset = downPointerInputChange.position
}
}
// touch Move事件
// 滑动的时候，box随着手指的移动去移动
awaitPointerEventScope {
drag(downPointerInputChange.id, onDrag = {
touchOffset = it.position
})
}
// 在手指弹起的时候，才通过动画的形式，回到原点的位置
val dragUpOrCancelPointerInputChange = awaitPointerEventScope {
awaitDragOrCancellation(downPointerInputChange.id)
}
// 等于空，说明已经抬起
if (dragUpOrCancelPointerInputChange == null) {
launch {
touchOffset = Offset.Zero
}
}
}
}
}, onDraw = {
charList.forEachIndexed { index, char ->
drawText(
size = Size(width = offsetY, offsetY),
textMeasurer = textMeasure, text = "$char",
style = TextStyle(
fontWeight = if (touchLetterIndex.value == index) FontWeight.SemiBold else FontWeight.Medium,
color = if (touchLetterIndex.value == index) Color.Blue else Color(
0xFF333333
),
textAlign = TextAlign.Center,
fontSize = if (touchLetterIndex.value == index) 16.sp else 14.sp
),
topLeft = Offset(offsetX, offsetY * index),
)
}
})
//中间显示的大写字母
val textMeasurer1 = rememberTextMeasurer()
if (touchOffset.x != 0f && touchOffset.y != 0f && scrollLetter.value.isNotEmpty()) {
val annotatedString = AnnotatedString(
scrollLetter.value, spanStyle = SpanStyle(
fontWeight = FontWeight.Medium,
color = Color(0xFF333333),
fontSize = 20.sp,
)
)
val textLayoutResult = textMeasurer1.measure(text = annotatedString)
val textSize = textLayoutResult.size
Canvas(modifier = Modifier
.align(Alignment.Center)
.requiredSize(width = 50.dp, height = 50.dp), onDraw = {
//底部颜色
drawRoundRect(
color = Color(0xA403A9F4), cornerRadius = CornerRadius(10f, 10f)
)
//绘制字母
drawText(
textMeasurer = textMeasurer1,
text = annotatedString,
topLeft = Offset(
(size.width - textSize.width) / 2f,
(size.height - textSize.height) / 2f
)
)
})
}
}
}
}private fun getIndex(list: MutableList<ContactEntity>, letter: Char): Int {
val findIndex = list.indexOfFirst { contactEntity ->
contactEntity.letter == letter
}
return findIndex
}
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