Sometimes, you need to validate text input by user when the EditText lost focus. To detect when the EditText lost focus, you need to use the setOnFocusChangeListener(OnFocusChangeListener l) method. You pass an object of anonymous class that implements the OnFocusChangeListener interface. You override the onFocusChange(View v, boolean hasFocus) method to perform data validation. The v parameter is the view that generates the focus change event. The hasFocus parameter is true or false. It is true when the view is focused and it is false when the view lost focus.
The example application below displays an input box when the user name or password text box is leaving blank when it lost focus.
In the activity_main.xml file, you add one TextView, two EditTexts, and one Button as shown below.

<LinearLayout 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"
   tools:context=".MainActivity"
   android:orientation="vertical"
   >
   <TextView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="Log in"
      android:gravity="center_horizontal"
      android:textStyle="bold"

      />
   <EditText
      android:id="@+id/txtusername"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:hint="User name"
      android:inputType="text"
      />
   <EditText
      android:id="@+id/txtpassword"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:hint="Password"
      android:inputType="textPassword"
      />
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="OK"
      />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android= "http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="match_parent"
   android:layout_height="wrap_content">
   <TextView
      android:id="@+id/txtmessage"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:padding="10dp"
      android:layout_margin="10dp"
      android:textSize="16sp"
      />
   <LinearLayout
      android:orientation="horizontal"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_gravity="center_horizontal"

      >
      <EditText
        android:id="@+id/txtinput"
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:inputType="numberSigned"
        />
      <Button
        android:id="@+id/btdone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Done"
        android:layout_weight="1"
        />
   </LinearLayout>
</LinearLayout>

import android.app.Dialog;
import android.content.Context;
import android.graphics.Color;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      final EditText txtUserName=(EditText)findViewById(R.id.txtusername);
      final EditText txtPassword=(EditText)findViewById(R.id.txtpassword);
      txtUserName.setOnFocusChangeListener(new View.OnFocusChangeListener() {
        @Override
        public void onFocusChange(View v, boolean hasFocus) {
           if(!hasFocus){
              EditText txtUser=(EditText)v;
              String userName=txtUser.getText().toString();
              if(userName.trim().equals("")){
                showInputBox(MainActivity.this, "Please input user name",txtUser);
              }
           }
        }
      });
      txtPassword.setOnFocusChangeListener(new View.OnFocusChangeListener() {
        @Override
        public void onFocusChange(View v, boolean hasFocus) {
           if(!hasFocus){
              EditText txtPwd=(EditText)v;
              String password=txtPwd.getText().toString();
              if(password.trim().equals("")){
                showInputBox(MainActivity.this, "Please input password",txtPwd);
              }
           }
        }
      });
   }

   public void showInputBox(final Context context,String message,final EditText txt){
      // Create dialog instance
      final Dialog dialog = new Dialog(context);
      // Set dialog title
      dialog.setTitle("Input box");
      // Set dialog layout
      dialog.setContentView(R.layout.input_box);
      TextView tvMess=(TextView)dialog.findViewById(R.id.txtmessage);
      tvMess.setText(message);
      tvMess.setTextColor(Color.parseColor("#ff2222"));
      Button btDone=(Button)dialog.findViewById(R.id.btdone);
      final EditText txtInput=(EditText)dialog.findViewById(R.id.txtinput);
      txtInput.setText(txt.getText().toString());
      txtInput.setInputType(txt.getInputType());
      btDone.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
           txt.setText(txtInput.getText().toString());
           dialog.dismiss();
        }
      });
      dialog.show();
   }
}

Sound Muter & Flashlight

Free & Easy to use app for Android

Posted by: Dara | post date: 04-25-2015 | Subject: Android Apps Development