Android: Tapping one to six buttons continuously [one after another] to string together different results

Question

I have decided to work on an Android app that uses very similar technology to that of an app I have seen before. I wanted to string together multiple button presses to equat

Answer 1

Alright so I have given this a go, and I believe this will help you get down the path you are attempting given my current understanding of your requirements. I have been quite verbose in my commenting of the class, what I am doing, and why. I hope it is helpful and doesn't feel like pandering. It sounded maybe you were pretty new to Java and Android and I felt the added explanation might be useful.

I am sure there are edge cases and bugs that have been missed, but should be a good start.

Android Activity Class -- MainActivity.java

import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Queue;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

/**
 * TAG is typically used for the Log class if you want to see debug/error information in logcat
 */
public static final String TAG = MainActivity.class.getSimpleName();

/**
 * Constant to delay before attempting to resolve button presses to an input
 */
public static final int INPUT_HANDLE_DELAY_MS = 500;
/**
 * Buttons have naming convention button
 */
private Button mButton00;
private Button mButton10;
private Button mButton01;
private Button mButton11;
private Button mButton02;
private Button mButton12;

/**
 * Where we are going to store the input generated by button presses
 */
private EditText mEditText;

/**
 * Where the lookup based on ids is going to happen and convert it to a character
 */
private static Map mLookupMap;

/**
 * I am not 100% sure if this is needed, but because we will be attempting to write to the mInputQueue,
 * and read from it, i've created a lock
 */
private static final Object mLock = new Object();

/**
 * Where we are going to store the input generated by button presses
 */
private Queue mInputQueue= new LinkedList<>();

/**
 * Android Handler class to help with the timer, and executing our runnable to handle the
 * button resolution
 */
private Handler mHandler = new Handler();

/**
 * Runnable to cause the application to check if there is valid input
 */
private Runnable mHandleInputRunnable;

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

    // method call to initialize the lookup map
    initializeLookup();

    // Obtain all the references from the layout that we are going to need to use
    mEditText = (EditText) findViewById(R.id.edit_text);
    mButton00 = (Button) findViewById(R.id.button_0_0);
    mButton10 = (Button) findViewById(R.id.button_1_0);
    mButton01 = (Button) findViewById(R.id.button_0_1);
    mButton11 = (Button) findViewById(R.id.button_1_1);
    mButton02 = (Button) findViewById(R.id.button_0_2);
    mButton12 = (Button) findViewById(R.id.button_1_2);

    // above, the activity implements the OnClickListener interface, set the activity to handle
    // the clicks of all of the buttons
    mButton00.setOnClickListener(this);
    mButton10.setOnClickListener(this);
    mButton01.setOnClickListener(this);
    mButton11.setOnClickListener(this);
    mButton02.setOnClickListener(this);
    mButton12.setOnClickListener(this);

    // initialize the Runnable to do what we need it to do when we get a 'tick'
    mHandleInputRunnable = new Runnable() {
        @Override
        public void run() {
            handleAlarmTrigger();
        }
    };
}

@Override
public void onClick(View v) {
    if (null != mInputQueue) {
        synchronized (mLock) {
            mInputQueue.add(v.getId());
        }
    }
    resetHandler();
}

/**
 * Helper method to do the initialization of the map. Sorry about the order for the button
 * presses. They are a little sporadic, no real rhyme or reason.
 */
private void initializeLookup() {
    if (null != mLookupMap) {
        return;
    }

    mLookupMap = new HashMap<>();

    /*
    1 button characters, use String.valueOf() instead of buildStringFromIds() as there is only
    one id
     */
    mLookupMap.put(String.valueOf(R.id.button_0_0), "A");
    mLookupMap.put(String.valueOf(R.id.button_1_0), "B");
    mLookupMap.put(String.valueOf(R.id.button_0_1), "C");
    mLookupMap.put(String.valueOf(R.id.button_1_1), "D");
    mLookupMap.put(String.valueOf(R.id.button_0_2), "E");
    mLookupMap.put(String.valueOf(R.id.button_1_2), "F");

    /*
    2 button characters
     */

    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_1_0), "G");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_0_1), "H");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_1_1), "I");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_0_2), "J");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_1_2), "K");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_0_0), "L");

    /*
    3 button characters
     */
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_1_0, R.id.button_0_1), "M");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_0_1, R.id.button_0_2), "N");
    mLookupMap.put(buildStringFromIds(R.id.button_1_0, R.id.button_1_1, R.id.button_1_2), "O");
    mLookupMap.put(buildStringFromIds(R.id.button_1_0, R.id.button_0_1, R.id.button_1_2), "P");
    mLookupMap.put(buildStringFromIds(R.id.button_1_2, R.id.button_1_2, R.id.button_0_1), "Q");
    mLookupMap.put(buildStringFromIds(R.id.button_1_2, R.id.button_1_2, R.id.button_0_1), "R");

    /*
    4 button characters
     */
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_0_0, R.id.button_0_0, R.id.button_0_0), "S");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_1_0, R.id.button_0_1, R.id.button_1_0), "T");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_0_1, R.id.button_0_2, R.id.button_0_1), "U");
    mLookupMap.put(buildStringFromIds(R.id.button_1_0, R.id.button_1_1, R.id.button_1_2, R.id.button_1_1), "V");
    mLookupMap.put(buildStringFromIds(R.id.button_1_0, R.id.button_0_1, R.id.button_1_2, R.id.button_0_2), "W");
    mLookupMap.put(buildStringFromIds(R.id.button_1_2, R.id.button_1_2, R.id.button_0_1, R.id.button_1_2), "X");

    /*
    5 button characters
     */

    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_0_0, R.id.button_0_0, R.id.button_0_0, R.id.button_0_0), "Y");
    mLookupMap.put(buildStringFromIds(R.id.button_0_0, R.id.button_1_0, R.id.button_0_1, R.id.button_1_0, R.id.button_1_1), "Z");
}

/**
 * Helper method to poll all of the values out of the queue, and create a key. This may or may
 * not be a valid key into the map. It depends on the button presses.
 *
 * @param queue the input queue where we store the id correlating to the button that was pressed
 * @return String representing a key into the map
 */
private String buildStringFromQueue(Queue queue) {
    StringBuilder sb = new StringBuilder();
    if (null != queue) {
        Integer pollValue;
        synchronized (mLock) {
            while ((pollValue = queue.poll()) != null) {
                sb.append(pollValue);
            }
        }
    }
    return sb.toString();
}

/**
 * Helper method to turn 1 to many R.id.button* into a string for a key as a lookup for a character
 * value
 *
 * The "..." means that the method can accept 1 or more values of the defined type
 *
 * @param ids 1 or more ids
 * @return String representing the ids as key into the map
 */
private String buildStringFromIds(int... ids) {
    StringBuilder sb = new StringBuilder();
    for (int id : ids) {
        sb.append(id);
    }

    return sb.toString();
}

/**
 * Helper method that is called each time there is a button click to either start or re-start
 * the time before resolving input
 */
private void resetHandler() {
    // null checks for the values we will be operating on
    if (null != mHandler && null != mHandleInputRunnable) {
        /**
         * remove the current runnable the handler may/may not have set, and reset it with the
         * delay. This is essentially resetting the time before the app takes the button press
         * and tries to do a lookup in the map.
         */
        mHandler.removeCallbacks(mHandleInputRunnable);
        mHandler.postDelayed(mHandleInputRunnable, INPUT_HANDLE_DELAY_MS);
    }
}

/**
 * Helper method that is called from the Runnable to attempt to handle the input
 */
private void handleAlarmTrigger() {
    // just to be safe, always check the queue for null, and don't handle if empty. Also
    // we will be setting values on the EditText, ensure it is non-null as well
    if (null != mEditText &&
            null != mInputQueue &&
            !mInputQueue.isEmpty()) {

        // Obtain the key from the input we have stored. This will provide a look up into the
        // map
        String mapKey = buildStringFromQueue(mInputQueue);

        // only try and append this if it was a valid set of button presses, and the map
        // actually has a value
        if (null != mapKey &&
                !mapKey.isEmpty() &&
                mLookupMap.containsKey(mapKey)) {
            mEditText.append(mLookupMap.get(mapKey));
        }

        // remove all stored values from the queue so we may restart the button presses
        synchronized (mLock) {
            mInputQueue.clear();
        }
    }
}
}

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Android Layout -- buttons.xml