kotlin高阶函数：简化常用的API

1.apply函数简化intent.putExtra():

val intent &＃61; Intent(this, MainActivity::class.java).apply { putExtra("param1","data1")putExtra("param2","data2")}startActivity(intent)

2.简化SharedPreferences:

fun SharedPreferences.open(block: SharedPreferences.Editor.() -> Unit) {val editor &＃61; edit()editor.block()editor.apply()}使用&＃xff1a;getSharedPreferences("data", Context.MODE_PRIVATE).open {putString("haha", "llaa")putBoolean("married", false)}

3.简化ContentValues:

fun cvOf(vararg pairs: Pair) &＃61; ContentValues().apply {for(pair in pairs){val key &＃61; pair.firstval value &＃61; pair.secondwhen(value){is Int -> put(key, value)is Long -> put(key, value)is Short -> put(key, value)is Float -> put(key, value)is Double -> put(key, value)is Boolean -> put(key, value)is String -> put(key, value)is Byte -> put(key, value)is ByteArray -> put(key, value)null -> putNull(key)}}}

4.懒加载技术实现lazy():

fun later(block: () -> T) &＃61; Later(block)class Later(val block: () -> T){var value: Any? &＃61; nulloperator fun getValue(any: Any?, prop: KProperty<*>): T{if (value &＃61;&＃61; null){value &＃61; block}return value as T}}使用&＃xff1a;val haha:String by later {"hhaa"}

5.泛型实化简化startActivity()并附带intent传值

inline fun startActivity(context: Context, block: Intent.() -> Unit){val intent &＃61; Intent(context, T::class.java)intent.block()context.startActivity(intent)}
使用&＃xff1a;startActivity(this){putExtra("haha","1111")putExtra("hahaaaa","1111")}

6.简化N个数的最大值最小值&＃xff1a;

fun > MyMax(vararg nums: T): T{if (nums.isEmpty()) throw RuntimeException("params can not be empty")var maxNum &＃61; nums[0]for (num in nums){if (num > maxNum){maxNum &＃61; num}}return maxNum} 使用&＃xff1a;val a &＃61; 1val b &＃61; 3val c &＃61; 2val largest &＃61; MyMax(a,b,c)

7.简化Toast&＃xff1a;

fun String.showToast(context: Context, duration: Int &＃61; Toast.LENGTH_SHORT){Toast.makeText(context, this, duration).show()}fun Int.showToast(context: Context, duration: Int &＃61; Toast.LENGTH_SHORT){Toast.makeText(context, this, duration).show()}用法&＃xff1a;"ahah".showToast(this, Toast.LENGTH_LONG)


8.简化Snackbar:

fun View.showSnackbar(text: String, actionText: String?&＃61;null, duration: Int &＃61; Snackbar.LENGTH_SHORT, block: (() -> Unit)? &＃61;null){val snackbar &＃61; Snackbar.make(this, text, duration)if (actionText !&＃61; null && block !&＃61; null){snackbar.setAction(actionText){block()}}snackbar.show()}fun View.showSnackbar(text: String, actionResId: Int?&＃61;null, duration: Int &＃61; Snackbar.LENGTH_SHORT, block: (() -> Unit)? &＃61;null){val snackbar &＃61; Snackbar.make(this, text, duration)if (actionResId !&＃61; null && block !&＃61; null){snackbar.setAction(actionResId){block()}}snackbar.show()}