记一次写Intent的扩展

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前言

写项目的时候经常会写到跳转Activiey，写到跳转Activit就一定会写到putExtra，就像下面那样

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intent.putExtra("a", item.a)
intent.putExtra("b", item.b)
intent.putExtra("c", item.c)

挺多哈，每次都要重复前面相同的内容，所以就想着能不能写个扩展来简写。

开始

我们最终实现是这样的：

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Intent(context, TestActivity::class.java)
  .putExtraVararg(
    "a" to item.a, 
    "b" to item.b, 
    "c" to item.c
  )

仿mapOf

经常用到mapOf()或者mutableMapOf()就会知道，里面是用了Pair类来生成Map的，所以受此启发，打算用Pair来作为参数实现，那么写的时候就应该是这样写，参数为可变参数类型：

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// 作为Intent的扩展
fun Intent.putExtraVararg(
    vararg extras: Pair<String, Any?>
): Intent {
    // 先省略
}

putExtra的第一个参数类型肯定是String类型，第二个参数的类型包括Bundle, Boolean, BooleanArray, Byte, ByteArray, Char, CharArray, String等等，所以就用Any类型，因为是可空的，所以加上?。

那么调用的时候，就是这样子的

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Intent(context, TestActivity::class.java)
    .putExtraVararg(
        "a" to item.a, 
        "b" to item.b, 
        "c" to item.c
    )

是不是就是一开始说的那样，对比平常写的是不是简单了很多。

参数类型匹配

写好了参数，那么就要进行对参数类型的匹配进行对应的putExtra。

vararg参数可以用forEach来循环对每个参数类型进行匹配：

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fun Intent.putExtraVararg(
    vararg extras: Pair<String, Any?>
): Intent {
    if (extras.isEmpty()) return this
    extras.forEach { (key, value) ->
        value ?: let {
            it.putExtra(key, it.toString())
            return@forEach
        }
        when (value) {
            is Bundle -> this.putExtra(key, value)
            is Boolean -> this.putExtra(key, value)
            is BooleanArray -> this.putExtra(key, value)
            is Byte -> this.putExtra(key, value)
            is ByteArray -> this.putExtra(key, value)
            is Char -> this.putExtra(key, value)
            is CharArray -> this.putExtra(key, value)
            is String -> this.putExtra(key, value)
            is CharSequence -> this.putExtra(key, value)
            is Double -> this.putExtra(key, value)
            is DoubleArray -> this.putExtra(key, value)
            is Float -> this.putExtra(key, value)
            is FloatArray -> this.putExtra(key, value)
            is Int -> this.putExtra(key, value)
            is IntArray -> this.putExtra(key, value)
            is Long -> this.putExtra(key, value)
            is LongArray -> this.putExtra(key, value)
            is Short -> this.putExtra(key, value)
            is ShortArray -> this.putExtra(key, value)
            is Parcelable -> this.putExtra(key, value)
            is Serializable -> this.putExtra(key, value)
            else -> {
                throw IllegalArgumentException("Not support $value type ${value.javaClass}..")
            }
        }
    }
    return this
}

发现没有，还少了ArrayList<String>、ArrayList<CharSequence>、ArrayList<? extends Parcelable>这三个List的参数类型匹配，因为不能直接is来匹配对应的Array类型，在群里问过之后，才得出最终的方法，Array里面有一个匹配对应类型的扩展函数isArrayOf()：

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/**
 * Checks if array can contain element of type [T].
 */
@Suppress("REIFIED_TYPE_PARAMETER_NO_INLINE")
public fun <reified T : Any> Array<*>.isArrayOf(): Boolean =
    T::class.java.isAssignableFrom(this::class.java.componentType)

so，这样就简单了，我们先匹配Array，然后在匹配对应的ArrayList<String>、ArrayList<CharSequence>、ArrayList<? extends Parcelable>，最后在对应put方法那里用as：

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is Array<*> -> {
    @Suppress("UNCHECKED_CAST")
    when {
        value.isArrayOf<String>() -> {
            this.putStringArrayListExtra(key, value as ArrayList<String?>)
        }
        value.isArrayOf<CharSequence>() -> {
            this.putCharSequenceArrayListExtra(key, value as ArrayList<CharSequence?>)
        }
        value.isArrayOf<Parcelable>() -> {
            this.putParcelableArrayListExtra(key, value as ArrayList<out Parcelable?>)
        }
    }
}

这样就实现了不同Array类型的putExtra。

最终

最后完整的代码为

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fun Intent.putExtraVararg(
    vararg extras: Pair<String, Any?>
): Intent {
    if (extras.isEmpty()) return this
    extras.forEach {
        val key = it.first
        val value = it.second ?: let {
            it.putExtra(key, it.toString())
        }
    }
    extras.forEach { (key, value) ->
        value ?: let {
            it.putExtra(key, it.toString())
            return@forEach
        }
        when (value) {
            is Bundle -> this.putExtra(key, value)
            is Boolean -> this.putExtra(key, value)
            is BooleanArray -> this.putExtra(key, value)
            is Byte -> this.putExtra(key, value)
            is ByteArray -> this.putExtra(key, value)
            is Char -> this.putExtra(key, value)
            is CharArray -> this.putExtra(key, value)
            is String -> this.putExtra(key, value)
            is CharSequence -> this.putExtra(key, value)
            is Double -> this.putExtra(key, value)
            is DoubleArray -> this.putExtra(key, value)
            is Float -> this.putExtra(key, value)
            is FloatArray -> this.putExtra(key, value)
            is Int -> this.putExtra(key, value)
            is IntArray -> this.putExtra(key, value)
            is Long -> this.putExtra(key, value)
            is LongArray -> this.putExtra(key, value)
            is Short -> this.putExtra(key, value)
            is ShortArray -> this.putExtra(key, value)
            is Array<*> -> {
                @Suppress("UNCHECKED_CAST")
                when {
                    value.isArrayOf<String>() -> {
                        this.putStringArrayListExtra(key, value as ArrayList<String?>)
                    }
                    value.isArrayOf<CharSequence>() -> {
                        this.putCharSequenceArrayListExtra(key, value as ArrayList<CharSequence?>)
                    }
                    value.isArrayOf<Parcelable>() -> {
                        this.putParcelableArrayListExtra(key, value as ArrayList<out Parcelable?>)
                    }
                }
            }
            is Parcelable -> this.putExtra(key, value)
            is Serializable -> this.putExtra(key, value)
            else -> {
                throw IllegalArgumentException("Not support $value type ${value.javaClass}..")
            }
        }
    }
    return this
}

转成Java是这样的：

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public final class IntentExtKt {
   @NotNull
   public static final Intent putExtraVararg(@NotNull Intent $receiver, @NotNull Pair... extras) {
      Intrinsics.checkParameterIsNotNull($receiver, "receiver$0");
      Intrinsics.checkParameterIsNotNull(extras, "extras");
      if (extras.length == 0) {
         return $receiver;
      } else {
         Pair[] var3 = extras;
         int var4 = extras.length;

         int var5;
         Pair element$iv;
         boolean var8;
         String key;
         for(var5 = 0; var5 < var4; ++var5) {
            element$iv = var3[var5];
            var8 = false;
            key = (String)element$iv.getFirst();
            if (element$iv.getSecond() == null) {
               int var12 = false;
               $receiver.putExtra(key, $receiver.toString());
            }
         }

         var3 = extras;
         var4 = extras.length;

         for(var5 = 0; var5 < var4; ++var5) {
            element$iv = var3[var5];
            var8 = false;
            key = (String)element$iv.component1();
            Object value = element$iv.component2();
            if (value != null) {
               if (value instanceof Bundle) {
                  $receiver.putExtra(key, (Bundle)value);
               } else if (value instanceof Boolean) {
                  $receiver.putExtra(key, (Boolean)value);
               } else if (value instanceof boolean[]) {
                  $receiver.putExtra(key, (boolean[])value);
               } else if (value instanceof Byte) {
                  $receiver.putExtra(key, ((Number)value).byteValue());
               } else if (value instanceof byte[]) {
                  $receiver.putExtra(key, (byte[])value);
               } else if (value instanceof Character) {
                  $receiver.putExtra(key, (Character)value);
               } else if (value instanceof char[]) {
                  $receiver.putExtra(key, (char[])value);
               } else if (value instanceof String) {
                  $receiver.putExtra(key, (String)value);
               } else if (value instanceof CharSequence) {
                  $receiver.putExtra(key, (CharSequence)value);
               } else if (value instanceof Double) {
                  $receiver.putExtra(key, ((Number)value).doubleValue());
               } else if (value instanceof double[]) {
                  $receiver.putExtra(key, (double[])value);
               } else if (value instanceof Float) {
                  $receiver.putExtra(key, ((Number)value).floatValue());
               } else if (value instanceof float[]) {
                  $receiver.putExtra(key, (float[])value);
               } else if (value instanceof Integer) {
                  $receiver.putExtra(key, ((Number)value).intValue());
               } else if (value instanceof int[]) {
                  $receiver.putExtra(key, (int[])value);
               } else if (value instanceof Long) {
                  $receiver.putExtra(key, ((Number)value).longValue());
               } else if (value instanceof long[]) {
                  $receiver.putExtra(key, (long[])value);
               } else if (value instanceof Short) {
                  $receiver.putExtra(key, ((Number)value).shortValue());
               } else if (value instanceof short[]) {
                  $receiver.putExtra(key, (short[])value);
               } else if (value instanceof Object[]) {
                  if ((Object[])value instanceof String[]) {
                     $receiver.putStringArrayListExtra(key, (ArrayList)value);
                  } else if ((Object[])value instanceof CharSequence[]) {
                     $receiver.putCharSequenceArrayListExtra(key, (ArrayList)value);
                  } else if ((Object[])value instanceof Parcelable[]) {
                     $receiver.putParcelableArrayListExtra(key, (ArrayList)value);
                  }
               } else if (value instanceof Parcelable) {
                  $receiver.putExtra(key, (Parcelable)value);
               } else {
                  if (!(value instanceof Serializable)) {
                     throw (Throwable)(new IllegalArgumentException("Not support " + value + " type " + value.getClass() + ".."));
                  }

                  $receiver.putExtra(key, (Serializable)value);
               }
            } else {
               int var13 = false;
               $receiver.putExtra(key, $receiver.toString());
            }
         }

         return $receiver;
      }
   }
}

顺手写别的扩展

既然用到Intent的扩展，那么就顺手写下Activity的startActivity的扩展

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/**
 * 同Context的startActivity
 */
fun Context.toActivity(packageContext: Context?, cls: Class<*>, vararg extras: Pair<String, Any?>) {
    startActivity(Intent(packageContext, cls).putExtraVararg(*extras))
}
/**
 * 同Context的startActivity
 */
fun Context.toActivity(intent: Intent) {
    startActivity(intent)
}

调用的时候就是这样子的

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context.toActivity(
    context,
    SearchActivity::class.java,
    SearchActivity.SEARCH_TYPE to item.type,
    SearchActivity.SEARCH_UID to item.uid,
    SearchActivity.SEARCH_NAME to item.name,
    SearchActivity.SEARCH_KEY to item.key,
    SearchActivity.SEARCH_GROUP to item.group
)

总结

通过这次的扩展，也学到了关于Array的一些扩展函数，可以说是很美好了。