How to develop a soft keyboard for Android?

I would like to play around with some ideas and develop a soft keyboard for Android to replace the default one.

• Is there any general information about soft keyboard development for Android out there? Any best practices or guidelines?

• Can I do with my keyboard application pretty much anything I could do with a normal Android application?

• Can I do HTTP connections to synchronize keyboard data with a cloud DB and other phones I have?

• Can I open other windows/screens from a key press, e.g. to display a custom input interface different to a normal QWERTY one. If that doesn't work, can I use a pop-up dialog instead?

Some tips:

• Read this tutorial: Creating an Input Method
• clone this repo: LatinIME

About your questions:

An inputMethod is basically an Android Service, so yes, you can do HTTP and all the stuff you can do in a Service.

You can open Activities and dialogs from the InputMethod. Once again, it's just a Service.

I've been developing an IME, so ask again if you run into an issue.

Create Custom Key Board for Own EditText

Download Entire Code

In this post i Created Simple Keyboard which contains Some special keys like ( France keys ) and it's supported Capital letters and small letters and Number keys and some Symbols .

package sra.keyboard;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.view.View.OnClickListener;
import android.view.View.OnFocusChangeListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RelativeLayout;

public class Main extends Activity implements OnTouchListener, OnClickListener,
  OnFocusChangeListener {
 private EditText mEt, mEt1; // Edit Text boxes
 private Button mBSpace, mBdone, mBack, mBChange, mNum;
 private RelativeLayout mLayout, mKLayout;
 private boolean isEdit = false, isEdit1 = false;
 private String mUpper = "upper", mLower = "lower";
 private int w, mWindowWidth;
 private String sL[] = { "a", "b", "c", "d", "e", "f", "g", "h", "i", "j",
   "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w",
   "x", "y", "z", "ç", "à", "é", "è", "û", "î" };
 private String cL[] = { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J",
   "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W",
   "X", "Y", "Z", "ç", "à", "é", "è", "û", "î" };
 private String nS[] = { "!", ")", "'", "#", "3", "$", "%", "&", "8", "*",
   "?", "/", "+", "-", "9", "0", "1", "4", "@", "5", "7", "(", "2",
   "\"", "6", "_", "=", "]", "[", "<", ">", "|" };
 private Button mB[] = new Button[32];

 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  try {
   setContentView(R.layout.main);
   // adjusting key regarding window sizes
   setKeys();
   setFrow();
   setSrow();
   setTrow();
   setForow();
   mEt = (EditText) findViewById(R.id.xEt);
   mEt.setOnTouchListener(this);
   mEt.setOnFocusChangeListener(this);
   mEt1 = (EditText) findViewById(R.id.et1);

   mEt1.setOnTouchListener(this);
   mEt1.setOnFocusChangeListener(this);
   mEt.setOnClickListener(this);
   mEt1.setOnClickListener(this);
   mLayout = (RelativeLayout) findViewById(R.id.xK1);
   mKLayout = (RelativeLayout) findViewById(R.id.xKeyBoard);

  } catch (Exception e) {
   Log.w(getClass().getName(), e.toString());
  }

 }

 @Override
 public boolean onTouch(View v, MotionEvent event) {
  if (v == mEt) {
   hideDefaultKeyboard();
   enableKeyboard();

  }
  if (v == mEt1) {
   hideDefaultKeyboard();
   enableKeyboard();

  }
  return true;
 }

 @Override
 public void onClick(View v) {

  if (v == mBChange) {

   if (mBChange.getTag().equals(mUpper)) {
    changeSmallLetters();
    changeSmallTags();
   } else if (mBChange.getTag().equals(mLower)) {
    changeCapitalLetters();
    changeCapitalTags();
   }

  } else if (v != mBdone && v != mBack && v != mBChange && v != mNum) {
   addText(v);

  } else if (v == mBdone) {

   disableKeyboard();

  } else if (v == mBack) {
   isBack(v);
  } else if (v == mNum) {
   String nTag = (String) mNum.getTag();
   if (nTag.equals("num")) {
    changeSyNuLetters();
    changeSyNuTags();
    mBChange.setVisibility(Button.INVISIBLE);

   }
   if (nTag.equals("ABC")) {
    changeCapitalLetters();
    changeCapitalTags();
   }

  }

 }

 @Override
 public void onFocusChange(View v, boolean hasFocus) {
  if (v == mEt && hasFocus == true) {
   isEdit = true;
   isEdit1 = false;

  } else if (v == mEt1 && hasFocus == true) {
   isEdit = false;
   isEdit1 = true;

  }

 }

 private void addText(View v) {
  if (isEdit == true) {
   String b = "";
   b = (String) v.getTag();
   if (b != null) {
    // adding text in Edittext
    mEt.append(b);

   }
  }

  if (isEdit1 == true) {
   String b = "";
   b = (String) v.getTag();
   if (b != null) {
    // adding text in Edittext
    mEt1.append(b);

   }

  }

 }

 private void isBack(View v) {
  if (isEdit == true) {
   CharSequence cc = mEt.getText();
   if (cc != null && cc.length() > 0) {
    {
     mEt.setText("");
     mEt.append(cc.subSequence(0, cc.length() - 1));
    }

   }
  }

  if (isEdit1 == true) {
   CharSequence cc = mEt1.getText();
   if (cc != null && cc.length() > 0) {
    {
     mEt1.setText("");
     mEt1.append(cc.subSequence(0, cc.length() - 1));
    }
   }
  }
 }
 private void changeSmallLetters() {
  mBChange.setVisibility(Button.VISIBLE);
  for (int i = 0; i < sL.length; i++)
   mB[i].setText(sL[i]);
  mNum.setTag("12#");
 }
 private void changeSmallTags() {
  for (int i = 0; i < sL.length; i++)
   mB[i].setTag(sL[i]);
  mBChange.setTag("lower");
  mNum.setTag("num");
 }
 private void changeCapitalLetters() {
  mBChange.setVisibility(Button.VISIBLE);
  for (int i = 0; i < cL.length; i++)
   mB[i].setText(cL[i]);
  mBChange.setTag("upper");
  mNum.setText("12#");

 }

 private void changeCapitalTags() {
  for (int i = 0; i < cL.length; i++)
   mB[i].setTag(cL[i]);
  mNum.setTag("num");

 }

 private void changeSyNuLetters() {

  for (int i = 0; i < nS.length; i++)
   mB[i].setText(nS[i]);
  mNum.setText("ABC");
 }

 private void changeSyNuTags() {
  for (int i = 0; i < nS.length; i++)
   mB[i].setTag(nS[i]);
  mNum.setTag("ABC");
 }

 // enabling customized keyboard
 private void enableKeyboard() {

  mLayout.setVisibility(RelativeLayout.VISIBLE);
  mKLayout.setVisibility(RelativeLayout.VISIBLE);

 }

 // Disable customized keyboard
 private void disableKeyboard() {
  mLayout.setVisibility(RelativeLayout.INVISIBLE);
  mKLayout.setVisibility(RelativeLayout.INVISIBLE);

 }

 private void hideDefaultKeyboard() {
  getWindow().setSoftInputMode(
    WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);

 }

 private void setFrow() {
  w = (mWindowWidth / 13);
  w = w - 15;
  mB[16].setWidth(w);
  mB[22].setWidth(w + 3);
  mB[4].setWidth(w);
  mB[17].setWidth(w);
  mB[19].setWidth(w);
  mB[24].setWidth(w);
  mB[20].setWidth(w);
  mB[8].setWidth(w);
  mB[14].setWidth(w);
  mB[15].setWidth(w);
  mB[16].setHeight(50);
  mB[22].setHeight(50);
  mB[4].setHeight(50);
  mB[17].setHeight(50);
  mB[19].setHeight(50);
  mB[24].setHeight(50);
  mB[20].setHeight(50);
  mB[8].setHeight(50);
  mB[14].setHeight(50);
  mB[15].setHeight(50);

 }

 private void setSrow() {
  w = (mWindowWidth / 10);
  mB[0].setWidth(w);
  mB[18].setWidth(w);
  mB[3].setWidth(w);
  mB[5].setWidth(w);
  mB[6].setWidth(w);
  mB[7].setWidth(w);
  mB[26].setWidth(w);
  mB[9].setWidth(w);
  mB[10].setWidth(w);
  mB[11].setWidth(w);
  mB[26].setWidth(w);

  mB[0].setHeight(50);
  mB[18].setHeight(50);
  mB[3].setHeight(50);
  mB[5].setHeight(50);
  mB[6].setHeight(50);
  mB[7].setHeight(50);
  mB[9].setHeight(50);
  mB[10].setHeight(50);
  mB[11].setHeight(50);
  mB[26].setHeight(50);
 }

 private void setTrow() {
  w = (mWindowWidth / 12);
  mB[25].setWidth(w);
  mB[23].setWidth(w);
  mB[2].setWidth(w);
  mB[21].setWidth(w);
  mB[1].setWidth(w);
  mB[13].setWidth(w);
  mB[12].setWidth(w);
  mB[27].setWidth(w);
  mB[28].setWidth(w);
  mBack.setWidth(w);

  mB[25].setHeight(50);
  mB[23].setHeight(50);
  mB[2].setHeight(50);
  mB[21].setHeight(50);
  mB[1].setHeight(50);
  mB[13].setHeight(50);
  mB[12].setHeight(50);
  mB[27].setHeight(50);
  mB[28].setHeight(50);
  mBack.setHeight(50);

 }

 private void setForow() {
  w = (mWindowWidth / 10);
  mBSpace.setWidth(w * 4);
  mBSpace.setHeight(50);
  mB[29].setWidth(w);
  mB[29].setHeight(50);

  mB[30].setWidth(w);
  mB[30].setHeight(50);

  mB[31].setHeight(50);
  mB[31].setWidth(w);
  mBdone.setWidth(w + (w / 1));
  mBdone.setHeight(50);

 }

 private void setKeys() {
  mWindowWidth = getWindowManager().getDefaultDisplay().getWidth(); // getting
  // window
  // height
  // getting ids from xml files
  mB[0] = (Button) findViewById(R.id.xA);
  mB[1] = (Button) findViewById(R.id.xB);
  mB[2] = (Button) findViewById(R.id.xC);
  mB[3] = (Button) findViewById(R.id.xD);
  mB[4] = (Button) findViewById(R.id.xE);
  mB[5] = (Button) findViewById(R.id.xF);
  mB[6] = (Button) findViewById(R.id.xG);
  mB[7] = (Button) findViewById(R.id.xH);
  mB[8] = (Button) findViewById(R.id.xI);
  mB[9] = (Button) findViewById(R.id.xJ);
  mB[10] = (Button) findViewById(R.id.xK);
  mB[11] = (Button) findViewById(R.id.xL);
  mB[12] = (Button) findViewById(R.id.xM);
  mB[13] = (Button) findViewById(R.id.xN);
  mB[14] = (Button) findViewById(R.id.xO);
  mB[15] = (Button) findViewById(R.id.xP);
  mB[16] = (Button) findViewById(R.id.xQ);
  mB[17] = (Button) findViewById(R.id.xR);
  mB[18] = (Button) findViewById(R.id.xS);
  mB[19] = (Button) findViewById(R.id.xT);
  mB[20] = (Button) findViewById(R.id.xU);
  mB[21] = (Button) findViewById(R.id.xV);
  mB[22] = (Button) findViewById(R.id.xW);
  mB[23] = (Button) findViewById(R.id.xX);
  mB[24] = (Button) findViewById(R.id.xY);
  mB[25] = (Button) findViewById(R.id.xZ);
  mB[26] = (Button) findViewById(R.id.xS1);
  mB[27] = (Button) findViewById(R.id.xS2);
  mB[28] = (Button) findViewById(R.id.xS3);
  mB[29] = (Button) findViewById(R.id.xS4);
  mB[30] = (Button) findViewById(R.id.xS5);
  mB[31] = (Button) findViewById(R.id.xS6);
  mBSpace = (Button) findViewById(R.id.xSpace);
  mBdone = (Button) findViewById(R.id.xDone);
  mBChange = (Button) findViewById(R.id.xChange);
  mBack = (Button) findViewById(R.id.xBack);
  mNum = (Button) findViewById(R.id.xNum);
  for (int i = 0; i < mB.length; i++)
   mB[i].setOnClickListener(this);
  mBSpace.setOnClickListener(this);
  mBdone.setOnClickListener(this);
  mBack.setOnClickListener(this);
  mBChange.setOnClickListener(this);
  mNum.setOnClickListener(this);

 }

}

A good place to start is the sample application provided on the developer docs.

• Guidelines would be to just make it as usable as possible. Take a look at the others available on the market to see what you should be aiming for
• Yes, services can do most things, including internet; provided you have asked for those permissions
• You can open activities and do anything you like n those if you run into a problem with doing some things in the keyboard. For example HTC's keyboard has a button to open the settings activity, and another to open a dialog to change languages.

Take a look at other IME's to see what you should be aiming for. Some (like the official one) are open source.

first of all you should define an .xml file and make keyboard UI in it:

<?xml version="1.0" encoding="utf-8"?>
<Keyboard xmlns:android="http://schemas.android.com/apk/res/android"
android:keyWidth="12.50%p"
android:keyHeight="7%p">
<!--
android:horizontalGap="0.50%p"
android:verticalGap="0.50%p"
NOTE When we add a horizontalGap in pixels, this interferes with keyWidth in percentages adding up to 100%
NOTE When we have a horizontalGap (on Keyboard level) of 0, this make the horizontalGap (on Key level) to move from after the key to before the key... (I consider this a bug) 
-->
<Row>
    <Key android:codes="-5" android:keyLabel="remove"  android:keyEdgeFlags="left" />
    <Key android:codes="48"    android:keyLabel="0" />
    <Key android:codes="55006" android:keyLabel="clear" />
</Row>
<Row>
    <Key android:codes="49"    android:keyLabel="1"  android:keyEdgeFlags="left" />
    <Key android:codes="50"    android:keyLabel="2" />
    <Key android:codes="51"    android:keyLabel="3" />
</Row>
<Row>
    <Key android:codes="52"    android:keyLabel="4"  android:keyEdgeFlags="left" />
    <Key android:codes="53"    android:keyLabel="5" />
    <Key android:codes="54"    android:keyLabel="6" />
</Row>

<Row>
    <Key android:codes="55"    android:keyLabel="7"  android:keyEdgeFlags="left" />
    <Key android:codes="56"    android:keyLabel="8" />
    <Key android:codes="57"    android:keyLabel="9" />
</Row>

In this example you have 4 rows and in each row you have 3 keys. also you can put an icon in each key you want.

Then you should add xml tag in your activity UI like this:

<android.inputmethodservice.KeyboardView
        android:id="@+id/keyboardview1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@color/white"
        android:focusable="true"
        android:focusableInTouchMode="true"
        android:visibility="visible" />

Also in your .java activity file you should define the keyboard and assign it to a EditText:

CustomKeyboard mCustomKeyboard1 = new CustomKeyboard(this,
			R.id.keyboardview1, R.xml.horizontal_keyboard);
	mCustomKeyboard1.registerEditText(R.id.inputSearch);

This code asign inputSearch (which is a EditText) to your keyboard.

import android.app.Activity;
import android.inputmethodservice.Keyboard;
import android.inputmethodservice.KeyboardView;
import android.inputmethodservice.KeyboardView.OnKeyboardActionListener;
import android.text.Editable;
import android.text.InputType;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnFocusChangeListener;
import android.view.View.OnTouchListener;
import android.view.WindowManager;
import android.view.inputmethod.InputMethodManager;
import android.widget.EditText;


public class CustomKeyboard {

/** A link to the KeyboardView that is used to render this CustomKeyboard. */
private KeyboardView mKeyboardView;
/** A link to the activity that hosts the {@link #mKeyboardView}. */
private Activity mHostActivity;

/** The key (code) handler. */
private OnKeyboardActionListener mOnKeyboardActionListener = new OnKeyboardActionListener() {

	public final static int CodeDelete = -5; // Keyboard.KEYCODE_DELETE
	public final static int CodeCancel = -3; // Keyboard.KEYCODE_CANCEL
	public final static int CodePrev = 55000;
	public final static int CodeAllLeft = 55001;
	public final static int CodeLeft = 55002;
	public final static int CodeRight = 55003;
	public final static int CodeAllRight = 55004;
	public final static int CodeNext = 55005;
	public final static int CodeClear = 55006;

	@Override
	public void onKey(int primaryCode, int[] keyCodes) {
		// NOTE We can say '<Key android:codes="49,50" ... >' in the xml
		// file; all codes come in keyCodes, the first in this list in
		// primaryCode
		// Get the EditText and its Editable
		View focusCurrent = mHostActivity.getWindow().getCurrentFocus();
		if (focusCurrent == null
				|| focusCurrent.getClass() != EditText.class)
			return;
		EditText edittext = (EditText) focusCurrent;
		Editable editable = edittext.getText();
		int start = edittext.getSelectionStart();
		// Apply the key to the edittext
		if (primaryCode == CodeCancel) {
			hideCustomKeyboard();
		} else if (primaryCode == CodeDelete) {
			if (editable != null && start > 0)
				editable.delete(start - 1, start);
		} else if (primaryCode == CodeClear) {
			if (editable != null)
				editable.clear();
		} else if (primaryCode == CodeLeft) {
			if (start > 0)
				edittext.setSelection(start - 1);
		} else if (primaryCode == CodeRight) {
			if (start < edittext.length())
				edittext.setSelection(start + 1);
		} else if (primaryCode == CodeAllLeft) {
			edittext.setSelection(0);
		} else if (primaryCode == CodeAllRight) {
			edittext.setSelection(edittext.length());
		} else if (primaryCode == CodePrev) {
			View focusNew = edittext.focusSearch(View.FOCUS_BACKWARD);
			if (focusNew != null)
				focusNew.requestFocus();
		} else if (primaryCode == CodeNext) {
			View focusNew = edittext.focusSearch(View.FOCUS_FORWARD);
			if (focusNew != null)
				focusNew.requestFocus();
		} else { // insert character
			editable.insert(start, Character.toString((char) primaryCode));
		}
	}

	@Override
	public void onPress(int arg0) {
	}

	@Override
	public void onRelease(int primaryCode) {
	}

	@Override
	public void onText(CharSequence text) {
	}

	@Override
	public void swipeDown() {
	}

	@Override
	public void swipeLeft() {
	}

	@Override
	public void swipeRight() {
	}

	@Override
	public void swipeUp() {
	}
};

/**
 * Create a custom keyboard, that uses the KeyboardView (with resource id
 * <var>viewid</var>) of the <var>host</var> activity, and load the keyboard
 * layout from xml file <var>layoutid</var> (see {@link Keyboard} for
 * description). Note that the <var>host</var> activity must have a
 * <var>KeyboardView</var> in its layout (typically aligned with the bottom
 * of the activity). Note that the keyboard layout xml file may include key
 * codes for navigation; see the constants in this class for their values.
 * Note that to enable EditText's to use this custom keyboard, call the
 * {@link #registerEditText(int)}.
 * 
 * @param host
 *            The hosting activity.
 * @param viewid
 *            The id of the KeyboardView.
 * @param layoutid
 *            The id of the xml file containing the keyboard layout.
 */
public CustomKeyboard(Activity host, int viewid, int layoutid) {
	mHostActivity = host;
	mKeyboardView = (KeyboardView) mHostActivity.findViewById(viewid);
	mKeyboardView.setKeyboard(new Keyboard(mHostActivity, layoutid));
	mKeyboardView.setPreviewEnabled(false); // NOTE Do not show the preview
											// balloons
	mKeyboardView.setOnKeyboardActionListener(mOnKeyboardActionListener);
	// Hide the standard keyboard initially
	mHostActivity.getWindow().setSoftInputMode(
			WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);
}

/** Returns whether the CustomKeyboard is visible. */
public boolean isCustomKeyboardVisible() {
	return mKeyboardView.getVisibility() == View.VISIBLE;
}

/**
 * Make the CustomKeyboard visible, and hide the system keyboard for view v.
 */
public void showCustomKeyboard(View v) {
	mKeyboardView.setVisibility(View.VISIBLE);
	mKeyboardView.setEnabled(true);
	if (v != null)
		((InputMethodManager) mHostActivity
				.getSystemService(Activity.INPUT_METHOD_SERVICE))
				.hideSoftInputFromWindow(v.getWindowToken(), 0);
}

/** Make the CustomKeyboard invisible. */
public void hideCustomKeyboard() {
	mKeyboardView.setVisibility(View.GONE);
	mKeyboardView.setEnabled(false);
}

/**
 * Register <var>EditText<var> with resource id <var>resid</var> (on the
 * hosting activity) for using this custom keyboard.
 * 
 * @param resid
 *            The resource id of the EditText that registers to the custom
 *            keyboard.
 */
public void registerEditText(int resid) {
	// Find the EditText 'resid'
	EditText edittext = (EditText) mHostActivity.findViewById(resid);
	// Make the custom keyboard appear
	edittext.setOnFocusChangeListener(new OnFocusChangeListener() {
		// NOTE By setting the on focus listener, we can show the custom
		// keyboard when the edit box gets focus, but also hide it when the
		// edit box loses focus
		@Override
		public void onFocusChange(View v, boolean hasFocus) {
			if (hasFocus)
				showCustomKeyboard(v);
			else
				hideCustomKeyboard();
		}
	});
	edittext.setOnClickListener(new OnClickListener() {
		// NOTE By setting the on click listener, we can show the custom
		// keyboard again, by tapping on an edit box that already had focus
		// (but that had the keyboard hidden).
		@Override
		public void onClick(View v) {
			showCustomKeyboard(v);
		}
	});
	// Disable standard keyboard hard way
	// NOTE There is also an easy way:
	// 'edittext.setInputType(InputType.TYPE_NULL)' (but you will not have a
	// cursor, and no 'edittext.setCursorVisible(true)' doesn't work )
	edittext.setOnTouchListener(new OnTouchListener() {
		@Override
		public boolean onTouch(View v, MotionEvent event) {
			EditText edittext = (EditText) v;
			int inType = edittext.getInputType(); // Backup the input type
			edittext.setInputType(InputType.TYPE_NULL); // Disable standard
														// keyboard
			edittext.onTouchEvent(event); // Call native handler
			edittext.setInputType(inType); // Restore input type
			return true; // Consume touch event
		}
	});
	// Disable spell check (hex strings look like words to Android)
	edittext.setInputType(edittext.getInputType()
			| InputType.TYPE_TEXT_FLAG_NO_SUGGESTIONS);
}

}

// NOTE How can we change the background color of some keys (like the
// shift/ctrl/alt)?
// NOTE What does android:keyEdgeFlags do/mean