Custom View, detect touch to toggle color

This example implement a custom view, it have only one function, toggle color if user touched.


Create MyView.java

package com.example.androidtouchview;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class MyView extends View {

 boolean touchOn;

 public MyView(Context context) {
  super(context);
  init();
 }

 public MyView(Context context, AttributeSet attrs) {
  super(context, attrs);
  init();
 }

 public MyView(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  init();
 }

 private void init() {
  touchOn = false;
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec),
    MeasureSpec.getSize(heightMeasureSpec));
 }

 @Override
 protected void onDraw(Canvas canvas) {
  if (touchOn) {
   canvas.drawColor(Color.RED);
  } else {
   canvas.drawColor(Color.GRAY);
  }
 }

 @Override
 public boolean onTouchEvent(MotionEvent event) {
  super.onTouchEvent(event);
  
  int action = event.getAction();
  
  if(action == MotionEvent.ACTION_DOWN){
   touchOn = !touchOn;
   invalidate();
   return true;
  }
  
  return false;
 }

}

Modify /res/layout/activity_main.xml to include the custom view.

<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.example.androidtouchview.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal">
        
        <com.example.androidtouchview.MyView 
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:layout_margin="10dp"/>
        <com.example.androidtouchview.MyView 
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="2"
            android:layout_margin="10dp"/>
        
    </LinearLayout>
    
</LinearLayout>

Keep using the auto generated MainActivity.java

You will be warned "MyView overrides onTouchEvent but not performClick" on onTouchEvent() method, read next post to fix it.