Xposed的beforeHookedMethod、afterHookedMethod、replaceHookedMethod使用区别

2019-12-18 15:49:57  阅读 304 次 评论 0 条

原文说明

	/**
	 * Called before the invocation of the method.
	 *
	 * <p>You can use {@link MethodHookParam#setResult} and {@link MethodHookParam#setThrowable}
	 * to prevent the original method from being called.
	 *
	 * <p>Note that implementations shouldn't call {@code super(param)}, it's not necessary.
	 *
	 * @param param Information about the method call.
	 * @throws Throwable Everything the callback throws is caught and logged.
	 */
	protected void beforeHookedMethod(MethodHookParam param) throws Throwable {}

	/**
	 * Called after the invocation of the method.
	 *
	 * <p>You can use {@link MethodHookParam#setResult} and {@link MethodHookParam#setThrowable}
	 * to modify the return value of the original method.
	 *
	 * <p>Note that implementations shouldn't call {@code super(param)}, it's not necessary.
	 *
	 * @param param Information about the method call.
	 * @throws Throwable Everything the callback throws is caught and logged.
	 */
	protected void afterHookedMethod(MethodHookParam param) throws Throwable {}

	/**
	 * Shortcut for replacing a method completely. Whatever is returned/thrown here is taken
	 * instead of the result of the original method (which will not be called).
	 *
	 * <p>Note that implementations shouldn't call {@code super(param)}, it's not necessary.
	 *
	 * @param param Information about the method call.
	 * @throws Throwable Anything that is thrown by the callback will be passed on to the original caller.
	 */
	@SuppressWarnings("UnusedParameters")
	protected abstract Object replaceHookedMethod(MethodHookParam param) throws Throwable;

翻译及总结

beforeHookedMethod 会在调用原方法前执行,如果使用setResult则跳过原方法,并返回setResult参数中的值。

afterHookedMethod 会在调用原方法后执行,setResult可改变返回值

replaceHookedMethod 会完全替换原方法,即原方法不执行,且返回值可以直接return,setResult不生效。


代码验证

需要被Hook的代码

至于返回值为什么用Integer ,因为在测试replaceHookedMethod的时候,给 int 赋 null 会崩……而 final是为了顺便验证下这个关键字会不会影响hook。

private void test(){
    Integer ret = hkBefore(100);
    Log.d(TAG, "hkBefore ret:" + ret);

    ret = hkBeforeSetResult(200);
    Log.d(TAG, "hkBeforeSetResult ret:" + ret);

    ret = hkAfter(300);
    Log.d(TAG, "hkAfter ret:" + ret);

    ret = hkAfterSetResult(400);
    Log.d(TAG, "hkAfterSetResult ret:" + ret);

    ret = hkReplace(500);
    Log.d(TAG, "hkReplace ret:" + ret);

    ret = hkReplaceReturn(600);
    Log.d(TAG, "hkReplaceReturn ret:" + ret);

    ret = hkReplaceSetResult(700);
    Log.d(TAG, "hkReplaceSetResult ret:" + ret);
}

public final Integer hkBefore(int a){
    Log.d(TAG, "————————————————————————hkBefore print:" + a);

    return a;
}

public final Integer hkBeforeSetResult(int a){
    Log.d(TAG, "————————————————————————hkBeforeSetResult print:" + a);

    return a;
}
public final Integer hkAfter(int a){
    Log.d(TAG, "————————————————————————hkAfter print:" + a);

    return a;
}
public final Integer hkAfterSetResult(int a){
    Log.d(TAG, "————————————————————————hkAfterSetResult print:" + a);

    return a;
}

public final Integer hkReplace(int a){
    Log.d(TAG, "————————————————————————hkReplace print:" + a);

    return a;
}

public final Integer hkReplaceReturn(int a){
    Log.d(TAG, "————————————————————————hkReplaceReturn print:" + a);

    return a;
}

public final Integer hkReplaceSetResult(int a){
    Log.d(TAG, "————————————————————————hkReplaceSetResult print:" + a);

    return a;
}

xposed模块

public class XMain implements IXposedHookLoadPackage {
    private final String TAG = "XposedMain";

    @Override
    public void handleLoadPackage(XC_LoadPackage.LoadPackageParam loadPackageParam) throws Throwable {
        Log.d(TAG, "hook app: " + loadPackageParam.packageName);

        if (loadPackageParam.packageName.equals("com.bloguan.democity")) {
            Log.d(TAG, "hook ");

            XposedHelpers.findAndHookMethod("com.bloguan.democity.demo.DTest", loadPackageParam.classLoader, "hkBefore", int.class, new XC_MethodHook() {
                @Override
                protected void beforeHookedMethod(MethodHookParam param) throws Throwable {
                    int a = (int) param.args[0];
                    param.args[0] = a + 1;
                }
            });

            XposedHelpers.findAndHookMethod("com.bloguan.democity.demo.DTest", loadPackageParam.classLoader, "hkBeforeSetResult", int.class, new XC_MethodHook() {
                @Override
                protected void beforeHookedMethod(MethodHookParam param) throws Throwable {
                    int a = (int) param.args[0];
                    param.args[0] = a + 1;
                    param.setResult(a + 2);
                }
            });

            XposedHelpers.findAndHookMethod("com.bloguan.democity.demo.DTest", loadPackageParam.classLoader, "hkAfter", int.class, new XC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    int a = (int) param.args[0];
                    param.args[0] = a + 1;
                }
            });

            XposedHelpers.findAndHookMethod("com.bloguan.democity.demo.DTest", loadPackageParam.classLoader, "hkAfterSetResult", int.class, new XC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    int a = (int) param.args[0];
                    param.args[0] = a + 1;
                    param.setResult(a + 2);
                }
            });

            XposedHelpers.findAndHookMethod("com.bloguan.democity.demo.DTest", loadPackageParam.classLoader, "hkReplace", int.class, new XC_MethodReplacement() {
                @Override
                protected Object replaceHookedMethod(MethodHookParam param) throws Throwable {

                    return null;
                }
            });

            XposedHelpers.findAndHookMethod("com.bloguan.democity.demo.DTest", loadPackageParam.classLoader, "hkReplaceReturn", int.class, new XC_MethodReplacement() {
                @Override
                protected Object replaceHookedMethod(MethodHookParam param) throws Throwable {
                    int a = (int) param.args[0];
                    return a + 1;
                }
            });

            XposedHelpers.findAndHookMethod("com.bloguan.democity.demo.DTest", loadPackageParam.classLoader, "hkReplaceSetResult", int.class, new XC_MethodReplacement() {
                @Override
                protected Object replaceHookedMethod(MethodHookParam param) throws Throwable {
                    int a = (int) param.args[0];
                    param.args[0] = a + 1;
                    param.setResult(a + 2);
                    return a + 3;
                }
            });

            Log.d(TAG, "hook success ");

        }
    }
}

xposed模块安装过程就不赘述了,既然有此一问,说明xposed已经用上了。

执行结果

12-18 16:20:22.878 2054-2054/com.bloguan.democity D/TEST: ————————————————————————hkBefore print:101
12-18 16:20:22.883 2054-2054/com.bloguan.democity D/TEST: hkBefore ret:101
12-18 16:20:22.883 2054-2054/com.bloguan.democity D/TEST: hkBeforeSetResult ret:202
12-18 16:20:22.883 2054-2054/com.bloguan.democity D/TEST: ————————————————————————hkAfter print:300
12-18 16:20:22.884 2054-2054/com.bloguan.democity D/TEST: hkAfter ret:300
12-18 16:20:22.884 2054-2054/com.bloguan.democity D/TEST: ————————————————————————hkAfterSetResult print:400
12-18 16:20:22.884 2054-2054/com.bloguan.democity D/TEST: hkAfterSetResult ret:402
12-18 16:20:22.884 2054-2054/com.bloguan.democity D/TEST: hkReplace ret:null
12-18 16:20:22.884 2054-2054/com.bloguan.democity D/TEST: hkReplaceReturn ret:601
12-18 16:20:22.884 2054-2054/com.bloguan.democity D/TEST: hkReplaceSetResult ret:703

打印不算太乱吧 = =

结论即上面说的,具体流程各位可以自己细看。

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