Android Kotlin

Android-Notes

安卓笔记

Posted by Ryan Yim on 2021-01-21
Estimated Reading Time 6 Minutes
Words 1.2k In Total
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Android

Activity跳转Fragment

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binding.fab.setOnClickListener { view ->
    // 跳转fragment界面(方法1) 这个只能跳转界面，没有实际功能
    setContentView(R.layout.fragment_qr_scanner)
    // 跳转fragment界面(方法2 建议的) 这个可以跳转代码（当你fragment从依赖包继承的时候）
    supportFragmentManager.beginTransaction().add(android.R.id.content, QrScannerFragment()).commit()
}

使用XXPermissions请求权限

https://github.com/getActivity/XXPermissions

首先添加远程仓库：

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dependencyResolutionManagement {
    repositories {
        // JitPack 远程仓库：https://jitpack.io
        maven { url 'https://jitpack.io' }
    }
}

# 如果是settings.gradle.kts：
dependencyResolutionManagement {
    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
    repositories {
        google()
        mavenCentral()
        // JitPack 远程仓库：https://jitpack.io
        maven {
            url = uri("https://jitpack.io")
        }
    }
}

然后引入依赖：

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android {
    // 支持 JDK 1.8 及以上
    compileOptions {
        targetCompatibility JavaVersion.VERSION_1_8
        sourceCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    // 权限请求框架：https://github.com/getActivity/XXPermissions
    implementation 'com.github.getActivity:XXPermissions:18.5'
}

# build.gradle.kts
// 权限请求框架：https://github.com/getActivity/XXPermissions
implementation("com.github.getActivity:XXPermissions:18.5")

使用：

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XXPermissions.with(this)
    // 申请单个权限
    .permission(Permission.CAMERA)
    .request(object : OnPermissionCallback {
      override fun onGranted(permissions: MutableList<String>, allGranted: Boolean) {
            if (!allGranted) {
                println("获取部分权限成功，但部分权限未正常授予")
                return
            }
            println("获取相机权限成功")
        }

        override fun onDenied(permissions: MutableList<String>, doNotAskAgain: Boolean) {
            if (doNotAskAgain) {
                println("被永久拒绝授权，请手动授予相机权限")
                // 如果是被永久拒绝就跳转到应用权限系统设置页面
                XXPermissions.startPermissionActivity(applicationContext, permissions)
            } else {
                println("获取相机权限失败")
            }
        }
    })

安卓启用储存

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直接在main activity中：
protected void onCreate(Bundle savedInstanceState) 中：
// 权限申请
        val permission = arrayOf(
            "android.permission.INTERNET",
            "android.permission.WRITE_EXTERNAL_STORAGE",
            "android.permission.READ_EXTERNAL_STORAGE"
        )
        Permissions.checkPermission(this, permission)

Permissions.kt

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package cn.rmshadows.weatherpost

import android.app.Activity
import android.content.pm.PackageManager
import androidx.core.app.ActivityCompat

object Permissions {
    fun checkPermission(activity: Activity, permission: Array<String?>) {
        val noPermission = arrayOfNulls<String>(permission.size)
        val j = 0
        for (i in permission.indices) {
            if (activity.checkSelfPermission(permission[i]!!) == PackageManager.PERMISSION_DENIED) {
                if (permission[i] != null) {
                    requestPermission(
                        arrayOf(
                            permission[i]
                        ), activity
                    )
                }
            }
        }
    }

    private fun requestPermission(s: Array<String?>, activity: Activity) {
        ActivityCompat.requestPermissions(activity, s, 100)
    }
}

启用视图绑定（Data Binding）

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kotlin项目：
build.gradle.kts
android {
    ...
    viewBinding {
        isEnabled = true
    }
}

或者build.gradle中：
android {
    ...
    viewBinding {
        enable = true
    }
}

二维码扫描CameraScan / ZXing-Lite

https://github.com/jenly1314/CameraScan

https://github.com/jenly1314/ZXingLite

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// CameraScan
implementation("com.github.jenly1314:camera-scan:1.0.1")

使用(TODO)：

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```

## Fragment之间的通讯

>https://developer.android.com/guide/fragments/communicate?hl=zh-cn#fragment-result
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## Fragment Dialog返回值到Fragment

DialogFragment中设置接口，然后在fragment实现接口以及传入context

class InputPortNumberDialogFragment : DialogFragment() {
// 在这里定义接口，在要显示DialogFragment的Fragment中实现这个接口
interface OnInputPortReceived {
fun onInputPortReceived(input: String)
}
// 接口
private var onInputReceived: OnInputPortReceived? = null

override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
    //为了样式统一和兼容性，可以使用 V7 包下的 AlertDialog.Builder
    val builder: AlertDialog.Builder = AlertDialog.Builder(requireContext())
    // 设置主题的构造方法
    val inflater: LayoutInflater = requireActivity().getLayoutInflater()
    val view: View = inflater.inflate(R.layout.fragment_input_dialog, null)
    builder.setView(view)
        .setMessage("请输入端口号（输入0默认54300）：")
        .setPositiveButton("确定") { dialog, which ->
            val et = view.findViewById<EditText>(R.id.inputEditText)
            var portInput:String = et.text.toString()
            if (! et.text.isEmpty()) {
                if (portInput.equals("0")){
                    portInput = "54300"
                }
                // 调用接口
                onInputReceived?.onInputPortReceived(portInput)
                dismiss() // 关闭对话框
            }
        }
        .setNegativeButton("取消", null)
    return builder.create()
}

// 接收从Fragment中传过来的接口
fun setOnInputListener(listener: OnInputPortReceived) {
    onInputReceived = listener
}

override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    return inflater.inflate(R.layout.fragment_input_dialog, container, false)
}

companion object {
    const val TAG = "getPortDialog"
}

}

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Fragment：

package cn.rmshadows.textsend.fragments

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.AdapterView
import android.widget.ArrayAdapter
import androidx.fragment.app.Fragment
import androidx.fragment.app.activityViewModels
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.ViewModelProvider
import androidx.lifecycle.lifecycleScope
import androidx.lifecycle.repeatOnLifecycle
import cn.rmshadows.textsend.R
import cn.rmshadows.textsend.databinding.FragmentServerBinding
import cn.rmshadows.textsend.viewmodels.ServerFragmentViewModel
import cn.rmshadows.textsend.viewmodels.TextsendViewModel
import kotlinx.coroutines.launch
import utils.Constant
import java.util.LinkedList

/**

  • A simple [Fragment] subclass as the second destination in the navigation.
    */
    class ServerFragment : Fragment(), InputPortNumberDialogFragment.OnInputPortReceived,
    InputIpAddressDialogFragment.OnInputIpReceived {
    private var _binding: FragmentServerBinding? = null
    private val TAG = Constant.TAG

    // This property is only valid between onCreateView and
    // onDestroyView.
    private val binding get() = _binding!!
    private lateinit var adapter: ArrayAdapter

    // https://developer.android.com/codelabs/basic-android-kotlin-training-shared-viewmodel?hl=zh-cn#4
    private val tsviewModel: TextsendViewModel by activityViewModels()
    private lateinit var viewModel: ServerFragmentViewModel

    // 实现接口
    override fun onInputIpReceived(input: String) {

     val oips = viewModel.uiState.value.netIps
 oips.removeLast()
 oips.add(input)
 oips.add(viewModel.CUSTOM_INPUT_FLAG)
 viewModel.update(input, null, oips, null, null)

    }

    override fun onInputPortReceived(input: String) {

     viewModel.update(null, input, null, null, null)

    }

    override fun onCreateView(

     inflater: LayoutInflater, container: ViewGroup?,
 savedInstanceState: Bundle?

    ): View {

     _binding = FragmentServerBinding.inflate(inflater, container, false)
 tsviewModel.update(true, null, null)
 viewModel = ViewModelProvider(this).get(ServerFragmentViewModel::class.java)
 return binding.root

    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {

     super.onViewCreated(view, savedInstanceState)

 binding.serverStartBtn.setOnLongClickListener {
     // 长按修改端口号
     val df = InputPortNumberDialogFragment()
     // 传入接口实现
     df.setOnInputListener(this)
     df.show(childFragmentManager, InputPortNumberDialogFragment.TAG)
     true
 }

    }

    override fun onDestroyView() {

     super.onDestroyView()
 _binding = null

    }
    }

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    `repeatOnLifecycle(Lifecycle.State.STARTED)`报错`The repeatOnLifecycle API should be used with viewLifecycleOwner`
     lifecycleScope.launch {
     repeatOnLifecycle(Lifecycle.State.STARTED) {
         viewModel.uiState.collect {
             binding.clientIpAddress.setText(it.serverIp)
             binding.clientPort.setText(it.serverPort.toString())
         }
     }
 }

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    解决：`lifecycleScope.launch`=>`viewLifecycleOwner.lifecycleScope.launch`

    viewLifecycleOwner.lifecycleScope.launch {

         repeatOnLifecycle(Lifecycle.State.STARTED) {
         viewModel.uiState.collect {
             binding.clientIpAddress.setText(it.serverIp)
             binding.clientPort.setText(it.serverPort.toString())
         }
     }
 }

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    # Kotlin

    ## Kotlin类变量

    >https://www.baeldung.com/kotlin/companion-object
    >
    >https://medium.com/@ansujain/kotlin-how-to-create-static-members-for-class-543d0f126f7c

    ```kotlin
    class ClassName {
        companion object {
            const val propertyName: String = "Something..."
            fun funName() {
                //...
            }
        }
    }

    class ClassName {
        companion object {
            const val propertyName: String = "Something..."
            fun funName() {
                //...
            }
        }
    }

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