按下相应的ImageButton后找不到方法

Question

I'm trying to create a simple rock, paper, scissors app but when the user selects the ImageButtons related to r,p, or s I get a

"Could not find method in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatImageButton with id"

When I comment out those methods in the java file I get an error in the xml saying that it

can't find the methods being called with the onClick attribute

and the errors go away once I remove the "//" So androidstudio seems to see the methods but for some reason it can't find them once they're there and being called? If it matters, this is the second activity in the app.(The other one being the main) This is a common error from what I've seen but I was unable to find a solution that worked for my situation.

This is my xml code(activity_rps.xml), I removed everything but the ImageButtons that are causing the problem

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ffffff"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.android.gamegroup.rps">

    <ImageButton
        android:id="@+id/rps_paper"
        android:layout_width="128dp"
        android:layout_height="128dp"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:background="@drawable/rps_paper"
        android:onClick="userChoicePaper" />

    <ImageButton
        android:id="@+id/rps_scissors"
        android:layout_width="128dp"
        android:layout_height="128dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:background="@drawable/rps_scissors"
        android:onClick="userChoiceScissors" />

    <ImageButton
        android:id="@+id/rps_rock"
        android:layout_width="128dp"
        android:layout_height="128dp"
        android:background="@drawable/rps_rock"
        android:onClick="userChoiceRock"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
</RelativeLayout>

This is my java code(rps.java). I've removed a lot that wasn't related to the problem and the sections that are commented out are from me trying to narrow down the issue.

package com.example.android.gamegroup;

import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;
import java.util.Random;

public class rps extends AppCompatActivity {
    //int userChoice, pcChoice, winner, userWinCount, pcWinCount;
    //ImageButton choiceRock = (ImageButton) findViewById(R.id.rps_rock);
    //ImageButton choicePaper = (ImageButton) findViewById(R.id.rps_paper);
    //ImageButton choiceScissors = (ImageButton)
findViewById(R.id.rps_scissors);

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

        //userWinCount = 0;
        //pcWinCount = 0;
    }

    // Generate a random integer ranging from 1 to 3 for 
    public void setPcChoice() {
        int randNum;
        Random randInt = new Random();
        randNum = randInt.nextInt(3) + 1;
        //pcChoice = randNum;
    }

    // Change userChoice to 1 for picking rock, assign pcChoice, assign 
    public void userChoiceRock(View view)
    {
        //choiceRock.setImageResource(R.drawable.rps_blue_rock);
        //userChoice = 1;
        setPcChoice();
        //setWinner();

    }

    // Change userChoice to 2 for picking paper, assign pcChoice, assign winner
    public void userChoicePaper(View view)
    {
        //choicePaper.setImageResource(R.drawable.rps_blue_paper);
        //userChoice = 2;
        setPcChoice();
        //setWinner();
    }

    // Change userChoice to 3 for picking scissors, assign pcChoice, assign winner******************
    public void userChoiceScissors(View view)
    {
        //choiceScissors.setImageResource(R.drawable.rps_blue_scissors);
        //userChoice = 3;
        setPcChoice();
        //setWinner();
    }

}

Answer 1

It is better to use OnClickListener in your java code in stead of using it in your xml . To do that you have to modify your rps.java as below:

public class rps extends AppCompatActivity {
    //int userChoice, pcChoice, winner, userWinCount, pcWinCount;
    ImageButton choiceRock;
    ImageButton choicePaper;
    ImageButton choiceScissors;

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

        choiceRock = (ImageButton) findViewById(R.id.rps_rock);
        choicePaper = (ImageButton) findViewById(R.id.rps_paper);
        choiceScissors = (ImageButton) findViewById(R.id.rps_scissors);

        choiceRock.setOnClickListener(new View.OnClickListener() {
            public void onClick(View arg0) {
               //choiceRock.setImageResource(R.drawable.rps_blue_rock);
               //userChoice = 1;
               setPcChoice();
               //setWinner();
            }
        });

        choicePaper.setOnClickListener(new View.OnClickListener() {
            public void onClick(View arg0) {
               //choicePaper.setImageResource(R.drawable.rps_blue_paper);
               //userChoice = 2;
               setPcChoice();
               //setWinner();
            }
        });

        choiceScissors.setOnClickListener(new View.OnClickListener() {
            public void onClick(View arg0) {
               //choiceScissors.setImageResource(R.drawable.rps_blue_scissors);
               //userChoice = 3;
               setPcChoice();
               //setWinner();
            }
        });

        //userWinCount = 0;
        //pcWinCount = 0;
    }

    public void setPcChoice() {
        int randNum;
        Random randInt = new Random();
        randNum = randInt.nextInt(3) + 1;
        //pcChoice = randNum;
    }
}

And finally, remove the android:onClick parts from the 3 ImageButton in your xml file.