android开发之Json文件的读写的示例代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  tools:context="com.cofox.functions.ReadWriteJsonData.ReadWriteJsonDataActivity">

  <Button
    android:id="@+id/btnSingleWJson"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="独立写Json文件" />

  <Button
    android:id="@+id/btnSingleRJson"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="独立读JSON文件" />

  <TextView
    android:id="@+id/ttvwJson"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:textSize="20sp"/>
</LinearLayout>

// 独立写Json文件
    btnSingleWJson.setOnClickListener {
}
// 独立读Json文件
    btnSingleRJson.setOnClickListener{
}

    // 独立写Json文件
    btnSingleWJson.setOnClickListener {
      // 判断有无写SD卡的权限
      if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
        //申请写 SD 卡的权限
        ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.WRITE_EXTERNAL_STORAGE), COFOX_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE)
      } else {
        saveSingleJson()
      }
    }

fun saveSingleJson(){
    Toast.makeText(this, "保存独立Json文件", Toast.LENGTH_LONG).show()
    //打开要写入的json文件
    val fos = FileOutputStream(jsonFile)
    //json数据
    val products = arrayListOf<Product>()
    products.add(Product("0001", "微服务核心服务端"))
    products.add(Product("0002", "平台管理android端"))
    products.add(Product("0003", "平台管理web端"))
    products.add(Product("0004", "企业用户android端"))
    products.add(Product("0005", "终端用户wx/android/web端"))
    products.add(Product("0006", "android全功能端"))
    products.add(Product("0007", "明月端"))
    //创建JsonWrite对象
    val writer = JsonWriter(OutputStreamWriter(fos, "utf-8"))
    writer.setIndent("  ")
    writer.beginArray()
    for (product in products){
      writer.beginObject()
      writer.name("id").value(product.id)
      writer.name("name").value(product.name)
      writer.endObject()
    }
    writer.endArray()
    writer.close()
  }

val jsonFile = "/sdcard/cofoxtest.json"

    // 独立读Json文件
    btnSingleRJson.setOnClickListener {
      val fis = FileInputStream(jsonFile)
      var reader = JsonReader(InputStreamReader(fis,"utf-8"))
      val products = ArrayList<Product>()
      reader.beginArray()
      while (reader.hasNext()){
        var id = ""
        var name = ""
        reader.beginObject()
        while (reader.hasNext()) {
          var field = reader.nextName()
          if (field.equals("id")){
            id = reader.nextString()
          }else if (field.equals("name")){
            name = reader.nextString()
          }else{
            reader.skipValue()
          }
        }
        reader.endObject()
        products.add(Product(id, name))
      }
      reader.endArray()
      reader.close()

      if (products != null) {
        var result = ""
        for (product in products) {
          result += "id:" + product.id + " name:" + product.name + "\n"
          ttvwJson.setText(result)
        }
      }
    }

  override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
    when (requestCode) {
      COFOX_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE -> {
        if (grantResults.size > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
          saveSingleJson()
        } else {
          Toast.makeText(this, "您拒绝了写入", Toast.LENGTH_LONG).show()
        }
      }
    }
  }