Compose实用知识整理

Box(Modifier.background(Color.Red)) {
    Box(Modifier
        .size(80.dp)
        .drawBehind {
            drawImage(
                bitmap.asImageBitmap(),
                srcSize = IntSize(bitmap.width, bitmap.height),
                dstSize = IntSize((density * 50).toInt(), (density * 50).toInt()),
                srcOffset = IntOffset.Zero,
                dstOffset = IntOffset.Zero
            )
        }) {
    }
    Text(text = "将图片绘制到成一个宽高50dp的情况")
}
Box(Modifier.background(Color.Red)) {
    Box(Modifier
        .size(80.dp)
        .drawBehind {
            val density = density.toInt()
            this.drawImage(
                bitmap.asImageBitmap(),
                srcOffset = IntOffset(15 * density, 15 * density),
                srcSize = IntSize(bitmap.width, bitmap.height),
                dstOffset = IntOffset(40 * density, 40 * density),
                dstSize = IntSize(density * 35, density * 35)
            )
            //                        dstSize = IntSize(density * 50, density * 50)
        }) {
    }
    Text(text = "将图片绘制到成一个宽高50dp的情况")
}
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singleLine = true, keyboardOptions = KeyboardOptions(
    keyboardType = KeyboardType.Text,
    imeAction = actionData.imeAction
), keyboardActions = KeyboardActions(
    onDone = {
        showToast("onDone")
    },
    onGo = {
        showToast("onGo")
    },
    onNext = {
        showToast("onNext")
    },
    onPrevious = {
        showToast("onPrevious")
    },
    onSearch = {
        showToast("onSearch")
    },
    onSend = {
        showToast("onSend")
    }
)
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@OptIn(ExperimentalComposeUiApi::class)
@Composable
fun KeyboardShowAndHide() {
    var text by remember {
        mutableStateOf("")
    }
    val requester = remember {//用于请求焦点的对象
        FocusRequester()
    }
    val keyboard = LocalSoftwareKeyboardController.current//用于操作键盘的对象
    LaunchedEffect(key1 = Unit, block = {
        requester.requestFocus()//首次进入和重组页面请求焦点
        keyboard?.show()//首次进入页面弹出键盘，注意必须先获取焦点才能弹出键盘成功
    })
    Column(
        Modifier
            .padding(top = 150.dp)
            .fillMaxSize(),
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        OutlinedTextField(
            value = text, onValueChange = {
                text = it
            }, modifier = Modifier.focusRequester(requester)//focusRequester方法表明让OutLineTextField可以获取焦点
        )
        Button(onClick = {
            requester.requestFocus()//替OutLineTextField请求焦点，一定要获取焦点才能操作键盘
            keyboard?.hide()//关闭键盘
        }, modifier = Modifier.fillMaxWidth()) {
            Text(text = "关闭键盘")
        }
    }
}
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@Composable
fun Test() {
    val model: TestModel = viewModel()
    CustomScaffold(title = "测试页面") {
        LazyColumn(content = {
            itemsIndexed(model.datas) { index: Int, data: Int ->
                Box(
                    Modifier
                        .padding(5.dp)
                        .fillMaxWidth()
                        .height(50.dp)
                        .border(width = 1.dp, color = Color.Green)
                        .clickable {
                            model.datas.add(index + 1)
                        },
                    contentAlignment = Alignment.Center
                ) {
                    if (index == model.datas.size - 1) {
                        Icon(
                            imageVector = Icons.Default.Add,
                            contentDescription = "",
                            tint = Color.Red
                        )
                    } else {
                        Text(text = data.toString())
                    }
                }
            }
        })
    }
}
class TestModel : ViewModel() {
    val datas = mutableStateListOf(0)
//    val datas = mutableListOf(0,1,2,3)
}
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@Composable
fun Back1(controller: NavHostController) {
    Column(
        Modifier
            .fillMaxSize()
            .background(Color.Red)
            .clickable {
                controller.popBackStack()
            }) {
        Text(text = "点击返回上一个页面")
        Text(text = "使用BackHandler实现返回键监听")
    }
    BackHandler(enabled = true) {
        Log.e("tag","返回键被点击")
    }
}
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@Composable
fun Back2(controller: NavHostController) {
    Column(
        Modifier
            .fillMaxSize()
            .background(Color.Green)
            .clickable {
                controller.popBackStack()
            }) {
        Text(text = "点击返回上一个页面")
        Text(text = "使用OnBackPressedDispatcher监听返回键被点击")
    }
    val callback = remember {
        object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
                log("回退键被点击")
                showToast("监听到返回键被点击监听")
            }
        }
    }
    val dispatcher = LocalOnBackPressedDispatcherOwner.current?.onBackPressedDispatcher
    DisposableEffect(key1 = Unit, effect = {
        dispatcher?.addCallback(callback)
        onDispose {
            callback.remove()
        }
    })
}
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@Composable
fun Modifier.avoidRepeatclickable(millis: Long = 500, onClick: () -> Unit): Modifier {
    var timeStamp by remember {
        mutableStateOf(0L)
    }
    return clickable {
        if (System.currentTimeMillis() - timeStamp > millis) {
            onClick()
            timeStamp = System.currentTimeMillis()
        }
    }
}
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androidx.activity:activity-compose:1.3.0
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val launcher = rememberLauncherForActivityResult(contract =object : ActivityResultContract<String, String>() {
        override fun parseResult(resultCode: Int, intent: Intent?): String {
           return intent?.getStringExtra("data")?:""
        }
        /**
         * @param compose向Compose中传的数据 ActivityResultContract<String, String>的第一个泛型
         */
        override fun createIntent(context: Context, input: String?): Intent {
            return Intent(context,GenerateActivityResultActivity::class.java).apply {
                putExtra("data",input)
            }
        }
    } , onResult = {result-> //result 是ActivityResultContract<String, String>第二个泛型
        activityResult = result
    })
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