J2V8Helper

As its name, this is a J2V8 helper library. It fixes 2 problems:

Changing value in js layer, no notify event will send to java layer.
Registering a lot of java fields and methods cost too much time and codes.

Installing

Step 1. In your root build.gradle, add the JitPack repository.

allprojects {
	repositories {
		...
        maven { url 'https://jitpack.io' }
    }
}

Step 2. Add the dependency

dependencies {
    implementation 'com.github.boybeak:J2V8Helper:Tag'
}

Usage

Step 1. Create V8

Create an v8 object as usual, and then, help it.

val v8 = V8.createV8Runtime()
J2V8Helper.help(v8)

After this, the J2V8Helper is helping this v8 runtime.

Step2. Register fields and methods

Native.kt

class Native(val v8: V8) {
    @V8Field
    val name = "Native for JS"
    @V8Method
    fun getPerson(): V8Object {
        val person = Person()
        return v8.createProxy(person)
    }
}

Mark the fields and methods with @V8Field and @V8Method. Then, register them.

val native = Native(v8)
val nativeV8 = V8Object(v8);
J2V8Helper.registerV8Fields(nativeV8, native)
J2V8Helper.registerV8Methods(nativeV8, native)
                
v8.add("Native", nativeV8)

Alternatively, if you are using Kotlin, you can use an extension method instead of registerV8Fields and registerV8Methods.

nativeV8.bindWith(native)

Step 3. Make a proxy if you need.

Let's look back to the code snippet Native.kt. It has a method named getPerson, in this method, return a V8Object that create by createProxy.

Now look deep into the Persion.kt.

class Person : V8Updatable {
    @V8Field(alias = "age", updatable = true)
    var age: Int = 0
        set(value) {
            field = value
            Log.d(TAG, "setAge to $value thread=${Thread.currentThread().name}")
        }

    override fun getKeys(): Array<String> {
        return arrayOf("phone")
    }

    override fun onV8Update(v8obj: V8Object, key: String, newValue: Any?, oldValue: Any?) {
        Log.d(TAG, "onV8Update(key=$key, value=$newValue)")
    }
}

The field age is marked by @V8Field, and has 2 options: alias and updatable.

alias: The field's name in JS layer;
update: Notify the field change when the value changed in JS layer.

Execute JS code with the v8 runtime.

const person = Native.getPerson();
person.age = 15

person.name = "John"
person.phone = "123456"

When the person.age value changed, in java layer, the setAge method will be called.

The next line is person.name= "john", and the Person has no field called name, so how to observe this value change?

The answer is using V8Updatable.

The Person class also implements V8Updatable interface.

V8Updatable has 3 key methods: onV8Update， getKeys and getUpdateStrategy.

onV8Update: Will be called when the value changed;
getKeys: The value change event will be cared or be ignored, it depends on the getUpdateStrategy return value, default value is empty array.
getUpdateStrategy: Has 2 enum value—— CARE and IGNORE, CARE means care about getKeys value changed, IGNORE means ingore getKeys value changed, default value is IGNORE.