Mixin 示例

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收录了较为常见的 Mixin 示例。此页面旨在帮助开发者快速学习 Mixin 的使用，建议在开始之前先查看 Mixin介绍。

注入到内部私有类的一个方法

使用 targets 参数并添加 $ 符号来指向内部类。

@Mixin(targets = "net.minecraft.client.render.block.BlockModelRenderer$AmbientOcclusionCalculator")
public class AmbientOcclusionCalculatorMixin {
    // 为所欲为 ^ v ^
}

在 Mixin 类中获取目标类实例对象

注意：应该避免像这样两次强转 this。如果你是要使用来自目标来的方法或字段，使用 @Shadow。如果方法或字段是来自目标类的父类，可以直接将你的这个 mixin 继承那个父类。 Mixin:

@Mixin(TargetClass.class)
public class MyMixin extends EveryThingThatTargetClassExtends implements EverythingThatTargetClassImplements {
  @Inject(method = "foo()V", at = @At("HEAD"))
  private void injected(CallbackInfo ci) {
    TargetClass thisObject = (TargetClass)(Object)this;
  }
}

注入到静态初始化代码块的开头

Mixin:

@Inject(method = "<clinit>", at = @At("HEAD"))
private void injected(CallbackInfo ci) {
    doSomething3();
}

结果:

static {
+   injected(new CallbackInfo(“<clinit>”, false));
    doSomething1();
    doSomething2();
}

注入在一个方法的开头

Mixin:

@Inject(method = "foo()V", at = @At("HEAD"))
private void injected(CallbackInfo ci) {
  doSomething4();
}

结果:

  public void foo() {
+   injected(new CallbackInfo("foo", false));
    doSomething1();
    doSomething2();
    doSomething3();
  }

注入到一个方法的结尾

Mixin:

@Inject(method = "foo()V", at = @At("TAIL"))
private void injected(CallbackInfo ci) {
  doSomething4();
}

结果:

  public void foo() {
    doSomething1();
    if (doSomething2()) {
      return;
    }
    doSomething3();
+   injected(new CallbackInfo("foo", false));
  }

注入到一个方法的返回之前

Mixin:

@Inject(method = "foo()V", at = @At("RETURN"))
private void injected(CallbackInfo ci) {
  doSomething4();
}

结果:

  public void foo() {
    doSomething1();
    if (doSomething2()) {
+     injected(new CallbackInfo("foo", false));
      return;
    }
    doSomething3();
+   injected(new CallbackInfo("foo", false));
  }

注入到一个方法调用之前

Mixin:

@Inject(method = "foo()V", at = @At(value = "INVOKE", target = "La/b/c/Something;doSomething()V"))
private void injected(CallbackInfo ci) {
  doSomething3();
}

结果:

  public void foo() {
    doSomething1();
    Something something = new Something();
+   injected(new CallbackInfo("foo", false));
    something.doSomething();
    doSomething2();
  }

注入到一个方法调用之后

Mixin:

@Inject(method = "foo()V", at = @At(value = "INVOKE", target = "La/b/c/Something;doSomething()V", shift = At.Shift.AFTER))
private void injected(CallbackInfo ci) {
  doSomething3();
}

结果:

  public void foo() {
    doSomething1();
    Something something = new Something();
    something.doSomething();
+   injected(new CallbackInfo("foo", false));
    doSomething2();
  }

使用偏移量注入

Mixin:

@Inject(method = "foo()V", at = @At(value = "INVOKE", target = "La/b/c/Something;doSomething()V", shift = At.Shift.BY, by = 2))
private void injected(CallbackInfo ci) {
  doSomething3();
}

结果:

  public void foo() {
    doSomething1();
    Something something = new Something();
    something.doSomething();
    doSomething2();
+   injected(new CallbackInfo("foo", false));
  }

使用 Slice 控制注入范围

Mixin:

@Inject(
  method = "foo()V",
  at = @At(
    value = "INVOKE",
    target = "La/b/c/Something;doSomething()V"
  ),
  slice = @Slice(
    from = @At(value = "INVOKE", target = "La/b/c/Something;doSomething2()V"),
    to = @At(value = "INVOKE", target = "La/b/c/Something;doSomething3()V")
  )
)
private void injected(CallbackInfo ci) {
  doSomething5();
}

结果:

  public class Something {
    public void foo() {
      this.doSomething1();
+     // 不会注入到此位置，因为它位于Slice范围之外
      this.doSomething();
      this.doSomething2();
+     injected(new CallbackInfo("foo", false));
      this.doSomething();
      this.doSomething3();
+     // 不会注入到此位置，因为它位于Slice范围之外
      this.doSomething();
      this.doSomething4();
    }
  }

注入并直接使当前方法返回

Mixin:

@Inject(method = "foo()V", at = @At("HEAD"), cancellable = true)
private void injected(CallbackInfo ci) {
  ci.cancel();
}

结果:

  public void foo() {
+   CallbackInfo ci = new CallbackInfo("foo", true);
+   injected(ci);
+   if (ci.isCancelled()) return;
    doSomething1();
    doSomething2();
    doSomething3();
  }

注入并使当前方法返回指定返回值

Mixin:

@Inject(method = "foo()I;", at = @At("HEAD"), cancellable = true)
private void injected(CallbackInfoReturnable<Integer> cir) {
  cir.setReturnValue(3);
}

结果:

  public int foo() {
+   CallbackInfoReturnable<Integer> cir = new CallbackInfoReturnable<Integer>("foo", true);
+   injected(cir);
+   if (cir.isCancelled()) return cir.getReturnValue();
    doSomething1();
    doSomething2();
    doSomething3();
    return 10;
  }

捕获局部变量

Mixin:

@Inject(method = "foo()V", at = @At(value = "TAIL"), locals = LocalCapture.CAPTURE_FAILHARD)
private void injected(CallbackInfo ci, TypeArg1 arg1) {
  //CAPTURE_FAILHARD: 如果计算局部变量与预期不符则抛出一个异常。
  arg1.doSomething4();
}

结果:

  public void foo() {
    TypeArg1 arg1 = getArg1();
    arg1.doSomething1();
    arg1.doSomething2();
    TypeArg2 arg2 = getArg2();
    arg2.doSomething3();
+   injected(new CallbackInfo("foo", false), arg1);
  }

捕获多个同一类型的局部变量中的一个

Mixin：

@Inject(method = "foo()V", at = @At(value = "TAIL"))
private void injected(CallbackInfo ci, @Local(ordinal = 2) TypeArg arg) {
  arg1.doSomething4();
}

结果：

  public void foo() {
    TypeArg arg1 = getArg1();
    TypeArg arg2 = getArg2();
    TypeArg arg3 = getArg3();
    TypeArg arg4 = getArg4();
    doSomething();
+   injected(new CallbackInfo("foo", false), arg3);
  }

修改返回值

Mixin:

@Inject(method = "foo()I;", at = @At("RETURN"), cancellable = true)
private void injected(CallbackInfoReturnable<Integer> cir) {
  cir.setReturnValue(cir.getReturnValue() * 3);
}

结果:

  public int foo() {
    doSomething1();
    doSomething2();
-   return doSomething3() + 7;
+   int i = doSomething3() + 7;
+   CallbackInfoReturnable<Integer> cir = new CallbackInfoReturnable<Integer>("foo", true, i);
+   injected(cir);
+   if (cir.isCancelled()) return cir.getReturnValue();
+   return i;
  }

重定向一个方法调用

Mixin:

@Redirect(method = "foo()V", at = @At(value = "INVOKE", target = "La/b/c/Something;doSomething(I)I"))
private int injected(Something something, int x) {
  return x + 3;
}

结果:

  public void foo() {
    doSomething1();
    Something something = new Something();
-   int i = something.doSomething(10);
+   int i = injected(something, 10);
    doSomething2();
  }

重定向获取到的字段值

Mixin:

@Redirect(method = "foo()V", at = @At(value = "FIELD", target = "La/b/c/Something;aaa:I", opcode = Opcodes.GETFIELD))
private int injected(Something something) {
  return 12345;
}

结果:

  public class Something {
    public int aaa;
    public void foo() {
      doSomething1();
-     if (this.aaa > doSomething2()) {
+     if (injected(this) > doSomething2()) {
        doSomething3();
      }
      doSomething4();
    }
  }

重定向一个字段的赋值

Mixin:

@Redirect(method = "foo()V", at = @At(value = "FIELD", target = "La/b/c/Something;aaa:I", opcode = Opcodes.PUTFIELD))
private void injected(Something something, int x) {
  something.aaa = x + doSomething5();
}

结果:

  public class Something {
    public int aaa;
    public void foo() {
      doSomething1();
-     this.aaa = doSomething2() + doSomething3();
+     inject(this, doSomething2() + doSomething3());
      doSomething4();
    }
  }

修改调用方法的一个参数

Mixin:

@ModifyArg(method = "foo()V", at = @At(value = "INVOKE", target = "La/b/c/Something;doSomething(ZIII)V"), index = 2)
private int injected(int x) {
  return x * 3;
}

结果:

  public void foo() {
    doSomething1();
    Something something = new Something();
-   something.doSomething(true, 1, 4, 5);
+   something.doSomething(true, 1, injected(4), 5);
    doSomething2();
  }

修改调用方法的多个参数

Mixin:

@ModifyArgs(method = "foo()V", at = @At(value = "INVOKE", target = "La/b/c/Something;doSomething(IDZ)V"))
private void injected(Args args) {
    int a0 = args.get(0);
    double a1 = args.get(1);
    boolean a2 = args.get(2);
    args.set(0, a0 + 3);
    args.set(1, a1 * 2.0D);
    args.set(2, !a2);
}

结果:

  public void foo() {
    doSomething1();
    Something something = new Something();
-   something.doSomething(3, 2.5D, true);
+   // 事实上，自动生成的 Args 子类是在运行时被创建的，
+   // 但是我们抹去了一些细节以便于理解。
+   Args args = new Args(new Object[] { 3, 2.5D, true });
+   injected(args);
+   something.doSomething(args.get(0), args.get(1), args.get(2));
    doSomething2();
  }

修改一个接收参数

Mixin:

@ModifyVariable(method = "foo(ZIII)V", at = @At("HEAD"), ordinal = 1)
private int injected(int y) {
  return y * 3;
}

结果:

  public void foo(boolean b, int x, int y, int z) {
+   y = injected(y);
    doSomething1();
    doSomething2();
    doSomething3();
  }

在赋值时修改一个局部变量

Mixin:

@ModifyVariable(method = "foo()V", at = @At("STORE"), ordinal = 1)
private double injected(double x) {
  return x * 1.5D;
}

结果:

  public void foo() {
    int i0 = doSomething1();
    double d0 = doSomething2();
-   double d1 = doSomething3() + 0.8D;
+   double d1 = injected(doSomething3() + 0.8D);
    double d2 = doSomething4();
  }

修改一个常量

Mixin:

@ModifyConstant(method = "foo()V", constant = @Constant(intValue = 4))
private int injected(int value) {
  return ++value;
}

结果:

  public void foo() {
-   for (int i = 0; i < 4; i++) {
+   for (int i = 0; i < injected(4); i++) {
      doSomething(i);
    }
  }