Android Button Control


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A Button is a Push-button which can be pressed, or clicked, by the user to perform an action.

Button

Button Attributes

Following are the important attributes related to Button control. You can check Android official documentation for complete list of attributes and related methods which you can use to change these attributes are run time.

Inherited from android.widget.TextView Class −

Attribute Description
android:autoText If set, specifies that this TextView has a textual input method and automatically corrects some common spelling errors.
android:drawableBottom This is the drawable to be drawn below the text.
android:drawableRight This is the drawable to be drawn to the right of the text.
android:editable If set, specifies that this TextView has an input method.
android:text This is the Text to display.

Inherited from android.view.View Class −

Attribute Description
android:background This is a drawable to use as the background.
android:contentDescription This defines text that briefly describes content of the view.
android:id This supplies an identifier name for this view,
android:onClick This is the name of the method in this View's context to invoke when the view is clicked.
android:visibility This controls the initial visibility of the view.

Example

This example will take you through simple steps to show how to create your own Android application using Linear Layout and Button.

Step Description
1 You will use Android studio IDE to create an Android application and name it as myapplication under a package com.example.saira_000.myapplication as explained in the Hello World Example chapter.
2 Modify src/MainActivity.java file to add a click event.
2 Modify the default content of res/layout/activity_main.xml file to include Android UI control.
3 No need to declare default string constants at string.xml, Android studio takes care of default string constants.
4 Run the application to launch Android emulator and verify the result of the changes done in the application.

Following is the content of the modified main activity file src/MainActivity.java. This file can include each of the fundamental lifecycle methods.

package com.example.saira_000.myapplication;

import android.content.Intent;
import android.net.Uri;
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.Toast;

public class MainActivity extends ActionBarActivity {
   Button b1,b2,b3;
   
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      
      b1=(Button)findViewById(R.id.button);
      b1.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            Toast.makeText(MainActivity.this,"YOUR MESSAGE",Toast.LENGTH_LONG).show();
         }
      });
   }
   
   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
      // Inflate the menu; this adds items to the action bar if it is present.
      getMenuInflater().inflate(R.menu.menu_main, menu);
      return true;
   }
   
   @Override
   public boolean onOptionsItemSelected(MenuItem item) {
      // Handle action bar item clicks here. The action bar will
      // automatically handle clicks on the Home/Up button, so long
      // as you specify a parent activity in AndroidManifest.xml.
      
      int id = item.getItemId();
      
      //noinspection SimplifiableIfStatement
      if (id == R.id.action_settings) {
         return true;
      }
      return super.onOptionsItemSelected(item);
   }
}

Following will be the content of res/layout/activity_main.xml file −

<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:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   android:paddingBottom="@dimen/activity_vertical_margin"
   tools:context=".MainActivity">
   
   <TextView
      android:id="@+id/textView1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Button Control"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true"
      android:textSize="30dp" />
      
   <TextView
      android:id="@+id/textView2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Tutorials point"
      android:textColor="#ff87ff09"
      android:textSize="30dp"
      android:layout_below="@+id/textView1"
      android:layout_centerHorizontal="true" />
      
   <ImageButton
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/imageButton"
      android:src="@drawable/abc"
      android:layout_below="@+id/textView2"
      android:layout_centerHorizontal="true" />
      
   <EditText
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/editText"
      android:layout_below="@+id/imageButton"
      android:layout_alignRight="@+id/imageButton"
      android:layout_alignEnd="@+id/imageButton" />
      
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Button"
      android:id="@+id/button"
      android:layout_alignTop="@+id/editText"
      android:layout_alignLeft="@+id/textView1"
      android:layout_alignStart="@+id/textView1"
      android:layout_alignRight="@+id/editText"
      android:layout_alignEnd="@+id/editText" />
      
</RelativeLayout>

Following will be the content of res/values/strings.xml to define these new constants −

<?xml version="1.0" encoding="utf-8"?>
<resources>
   <string name="app_name">myapplication</string>
   <string name="action_settings">Settings</string>
</resources>

Following is the default content of AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.guidemo4"
   android:versionCode="1"
   android:versionName="1.0" >
   
   <uses-sdk
      android:minSdkVersion="8"
      android:targetSdkVersion="22" />
      
   <application
      android:allowBackup="true"
      android:icon="@drawable/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >
      
      <activity
         android:name="com.example.guidemo4.MainActivity"
         android:label="@string/app_name" >
      
      <intent-filter>
         <action android:name="android.intent.action.MAIN" />
         <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
      
      </activity>
      
   </application>
</manifest>

Let's try to run your GUIDemo4 application. I assume you had created your AVD while doing environment setup. To run the app from Android Studio, open one of your project's activity files and click Run Eclipse Run Icon icon from the toolbar.Android Studio installs the app on your AVD and starts it and if everything is fine with your setup and application, it will display following Emulator window:

Android Button Control

The following screen will appear by clicking on Button −

Android Button Control

Exercise

I will recommend to try above example with different attributes of Button in Layout XML file as well at programming time to have different look and feel of the Button. Try to make it editable, change to font color, font family, width, textSize etc and see the result. You can also try above example with multiple Button controls in one activity.


android_user_interface_controls.htm

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