即将手机上的app的内容发送到PC上的frida python程序，然后处理后返回给app，然后app再做后续的流程，核心是理解send/recv函数

<TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="please input username and password"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />


    <EditText
        android:id="@+id/editText"
        android:layout_width="fill_parent"
        android:layout_height="40dp"
        android:hint="username"
        android:maxLength="20"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.095" />

    <EditText
        android:id="@+id/editText2"
        android:layout_width="fill_parent"
        android:layout_height="40dp"
        android:hint="password"
        android:maxLength="20"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.239" />

    <Button
        android:id="@+id/button"
        android:layout_width="100dp"
        android:layout_height="35dp"
        android:layout_gravity="right|center_horizontal"
        android:text="提交"
        android:visibility="visible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.745" />

public class MainActivity extends AppCompatActivity {

    EditText username_et;
    EditText password_et;
    TextView message_tv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        password_et = (EditText) this.findViewById(R.id.editText2);
        username_et = (EditText) this.findViewById(R.id.editText);
        message_tv = ((TextView) findViewById(R.id.textView));

        this.findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (username_et.getText().toString().compareTo("admin") == 0) {
                    message_tv.setText("You cannot login as admin");
                    return;
                }
                //hook target
                message_tv.setText("Sending to the server :" + Base64.encodeToString((username_et.getText().toString() + ":" + password_et.getText().toString()).getBytes(), Base64.DEFAULT));

            }
        });

    }
}

先分析问题，我的最终目标是让message_tv.setText可以"发送"username为admin的base64字符串。
那肯定是hook TextView.setText这个函数。

console.log("Script loaded successfully ");
Java.perform(function () {
    var tv_class = Java.use("android.widget.TextView");
    tv_class.setText.overload("java.lang.CharSequence").implementation = function (x) {
        var string_to_send = x.toString();
        var string_to_recv;
        send(string_to_send); // send data to python code
        recv(function (received_json_object) {
            string_to_recv = received_json_object.my_data
            console.log("string_to_recv: " + string_to_recv);
        }).wait(); //block execution till the message is received
        var my_string = Java.use("java.lang.String").$new(string_to_recv);
        this.setText(my_string);
    }
});

import time
import frida
import base64

def my_message_handler(message, payload):
    print(message)
    print(payload)
    if message["type"] == "send":
        print(message["payload"])
        data = message["payload"].split(":")[1].strip()
        print( 'message:', message)
        #data = data.decode("base64")
        #data = data
        data = str(base64.b64decode(data))
        print( 'data:',data)
        user, pw = data.split(":")
        print( 'pw:',pw)
        #data = ("admin" + ":" + pw).encode("base64")
        data = str(base64.b64encode(("admin" + ":" + pw).encode()))
        print( "encoded data:", data)
        script.post({"my_data": data})  # send JSON object
        print( "Modified data sent")

device = frida.get_usb_device()
pid = device.spawn(["myapplication.example.com.frida_demo"])
device.resume(pid)
time.sleep(1)
session = device.attach(pid)
with open("frida_demo2.js") as f:
    script = session.create_script(f.read())
script.on("message", my_message_handler)
script.load()
input()

参考链接：https://github.com/Mind0xP/Frida-Python-Binding