Reducing repetitive Android code

Question

How can I reduce the amount of repetitive code in my Android app? A lot of the code seems to be doing the same thing twice. I think that there is a more compact way to do this.

What are some ways that I can reduce lines of code in this program?
Is there a better way that I could write this program? I think that I am taking more steps than necessary.

The code is for this app.

package com.kerseykyle.easyhash;
import java.security.MessageDigest;
import android.os.Build;
import android.os.Bundle;
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Intent;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends Activity {
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 Share();
 Intent intent = getIntent();
 String action = intent.getAction();
 String type = intent.getType();
 if (Intent.ACTION_SEND.equals(action) && type != null) {
 if ("text/plain".equals(type)) {
 handleSendText(intent); // Handle text being sent
 } 
 } 
 EditText myTextBox = (EditText) findViewById(R.id.input);
 myTextBox.setSingleLine(true);
 myTextBox.addTextChangedListener(new TextWatcher() {
 public void afterTextChanged(Editable s) {
 }
 public void beforeTextChanged(CharSequence s, int start, int count,
 int after) {
 }
 @TargetApi(Build.VERSION_CODES.HONEYCOMB)
 public void onTextChanged(CharSequence s, int start, int before,
 int count) {
 String md5hash = CreateHash(s.toString(), "MD5");
 TextView md5 = (TextView) findViewById(R.id.md5);
 md5.setText(md5hash);
 md5.setTextIsSelectable(true);
 String sha1hash = CreateHash(s.toString(), "SHA-1");
 TextView sha1 = (TextView) findViewById(R.id.sha1);
 sha1.setText(sha1hash);
 sha1.setTextIsSelectable(true);
 String sha256hash = CreateHash(s.toString(), "SHA-256");
 TextView sha256 = (TextView) findViewById(R.id.sha256);
 sha256.setText(sha256hash);
 sha256.setTextIsSelectable(true);
 String sha512hash = CreateHash(s.toString(), "SHA-512");
 TextView sha512 = (TextView) findViewById(R.id.sha512);
 sha512.setText(sha512hash);
 sha512.setTextIsSelectable(true);
 }
 });
 }
 public static String CreateHash(String data, String function) {
 try {
 MessageDigest digest = MessageDigest.getInstance(function);
 byte[] hash = digest.digest(((String) data).getBytes("UTF-8"));
 StringBuffer hexString = new StringBuffer();
 for (int i = 0; i < hash.length; i++) {
 String hex = Integer.toHexString(0xff & hash[i]);
 if (hex.length() == 1)
 hexString.append('0');
 hexString.append(hex);
 }
 return hexString.toString();
 } catch (Exception ex) {
 throw new RuntimeException(ex);
 }
 }
 public void Share() {
 TextView md5 = (TextView) findViewById(R.id.md5);
 md5.setOnClickListener(new OnClickListener() {
 @Override
 public void onClick(View v) {
 // TODO Auto-generated method stub
 EditText myTextBox = (EditText) findViewById(R.id.input);
 String md5hash = CreateHash(myTextBox.getText().toString(),
 "MD5");
 Intent sendIntent = new Intent();
 sendIntent.setAction(Intent.ACTION_SEND);
 sendIntent.putExtra(Intent.EXTRA_TEXT, md5hash);
 sendIntent.setType("text/plain");
 startActivity(sendIntent);
 }
 });
 TextView sha1 = (TextView) findViewById(R.id.sha1);
 sha1.setOnClickListener(new OnClickListener() {
 @Override
 public void onClick(View v) {
 // TODO Auto-generated method stub
 EditText myTextBox = (EditText) findViewById(R.id.input);
 String sha1hash = CreateHash(myTextBox.getText().toString(),
 "SHA-1");
 Intent sendIntent = new Intent();
 sendIntent.setAction(Intent.ACTION_SEND);
 sendIntent.putExtra(Intent.EXTRA_TEXT, sha1hash);
 sendIntent.setType("text/plain");
 startActivity(sendIntent);
 }
 });
 TextView sha256 = (TextView) findViewById(R.id.sha256);
 sha256.setOnClickListener(new OnClickListener() {
 @Override
 public void onClick(View v) {
 // TODO Auto-generated method stub
 EditText myTextBox = (EditText) findViewById(R.id.input);
 String sha256hash = CreateHash(myTextBox.getText().toString(),
 "SHA-256");
 Intent sendIntent = new Intent();
 sendIntent.setAction(Intent.ACTION_SEND);
 sendIntent.putExtra(Intent.EXTRA_TEXT, sha256hash);
 sendIntent.setType("text/plain");
 startActivity(sendIntent);
 }
 });
 TextView sha512 = (TextView) findViewById(R.id.sha512);
 sha512.setOnClickListener(new OnClickListener() {
 @Override
 public void onClick(View v) {
 // TODO Auto-generated method stub
 EditText myTextBox = (EditText) findViewById(R.id.input);
 String sha512hash = CreateHash(myTextBox.getText().toString(),
 "SHA-512");
 Intent sendIntent = new Intent();
 sendIntent.setAction(Intent.ACTION_SEND);
 sendIntent.putExtra(Intent.EXTRA_TEXT, sha512hash);
 sendIntent.setType("text/plain");
 startActivity(sendIntent);
 }
 });
 {
 }
 }
 @TargetApi(Build.VERSION_CODES.HONEYCOMB)
 void handleSendText(Intent intent) {
 String sharedText = intent.getStringExtra(Intent.EXTRA_TEXT);
 if (sharedText != null) {
 EditText input = (EditText) findViewById(R.id.input);
 input.setText(sharedText);
 String md5hash = CreateHash(sharedText, "MD5");
 TextView md5 = (TextView) findViewById(R.id.md5);
 md5.setText(md5hash);
 md5.setTextIsSelectable(true);
 String sha1hash = CreateHash(sharedText, "SHA-1");
 TextView sha1 = (TextView) findViewById(R.id.sha1);
 sha1.setText(sha1hash);
 sha1.setTextIsSelectable(true);
 String sha256hash = CreateHash(sharedText, "SHA-256");
 TextView sha256 = (TextView) findViewById(R.id.sha256);
 sha256.setText(sha256hash);
 sha256.setTextIsSelectable(true);
 String sha512hash = CreateHash(sharedText, "SHA-512");
 TextView sha512 = (TextView) findViewById(R.id.sha512);
 sha512.setText(sha512hash);
 sha512.setTextIsSelectable(true);
 }
 } 
}

• abuzittin gillifirca: You should remove // TODO Auto-generated method stub as soon as you put any code in the method. It's just there to help you to find the method.

Answer 1

This type of problem is conveniently solved with a Strategy Pattern. But, first things first:

• you should search for efficient ways to convert bytes to hexadecimal-string values. This is a great solution I like....
• Unless you have no choice (you are using Patterns/Matchers) you should always use StringBuilder instead of StringBuffer
• The method CreateHash should not have a capital-letter to start with, it should rather be createHash

As for the Strategy Pattern.... In this case, you can create a class that listens for the text change, and updates the signature in the linked TextView. The same class listens for on-click on the TextView too. The class could have the signature

public abstract class HashDigestDisplay implements TextWatcher, OnClickListener {
 private final TextView view;
 private final MessageDigest digest;
 public HashDigestDisplay (TextView target, String digestName) throws NoSuchAlgorithmException {
 this.view = target;
 this.digest = MessageDigest.getInstance(digestName);
 this.view.setOnClickListener(this);
 }
 public void afterTextChanged(Editable s) {
 }
 public void beforeTextChanged(CharSequence s, int start, int count,
 int after) {
 }
 private String myDigest(String input) {
 digest.reset(); 
 byte[] hash = digest.digest(input.getBytes("UTF-8"));
 return bytesToHex(hash);
 }
 @TargetApi(Build.VERSION_CODES.HONEYCOMB)
 public void onTextChanged(CharSequence s, int start, int before, int count) {
 view.setText(myDigest(s.toString()));
 view.setTextIsSelectable(true);
 }
 @Override
 public void onClick(View v) {
 // TODO Auto-generated method stub
 EditText myTextBox = (EditText) findViewById(R.id.input);
 String hash = myDigest(myTextBox.getText().toString());
 Intent sendIntent = new Intent();
 sendIntent.setAction(Intent.ACTION_SEND);
 sendIntent.putExtra(Intent.EXTRA_TEXT, hash);
 sendIntent.setType("text/plain");
 startActivity(sendIntent);
 }
}

You can see the pattern that is emerging above. Obviously there are issues in the onClick method, but this is from copy/pasting your code.

Now, what you do in your onCreate() setup method is simply:

myTextBox.addTextChangedListener(
 new HashDigestDisplay((TextView) findViewById(R.id.md5), "MD5"));
myTextBox.addTextChangedListener(
 new HashDigestDisplay((TextView) findViewById(R.id.sha1), "SHA-1"));
....

After that, the system should be self-managing.

You only have one copy of the code, and the only things different about it are the name of the Digest and the target of the TextView.