Detect touched position on a ImageView

A custom ImageView is implemented, with onTouchEvent() method overrided. When user touched on the ImageView, the touch position will be passed to main activity and displayed on a TextView.

Implement the custom ImageView, TouchView.java.

package com.exercise.AndroidDetechTouch;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.ImageView;

public class TouchView extends ImageView {

 public TouchView(Context context) {
  super(context);
  // TODO Auto-generated constructor stub
 }

 public TouchView(Context context, AttributeSet attrs) {
  super(context, attrs);
  // TODO Auto-generated constructor stub
 }

 public TouchView(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  // TODO Auto-generated constructor stub
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  // TODO Auto-generated method stub
  setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec),
       MeasureSpec.getSize(heightMeasureSpec));
 }

 @Override
 public boolean onTouchEvent(MotionEvent event) {
  // TODO Auto-generated method stub
  
  
  switch(event.getAction()){
  case MotionEvent.ACTION_DOWN:
  case MotionEvent.ACTION_MOVE:
   float x = event.getX();
   float y = event.getY();
   ((AndroidDetechTouchActivity)getContext()).updateMsg("Touched@" + x + " : " + y);
   break;
  case MotionEvent.ACTION_UP:
   ((AndroidDetechTouchActivity)getContext()).updateMsg("");
   break;
  }
  
  return true;
 }

}

Modify the main activity to add updateMsg() method. It will be called from custom ImageView.

package com.exercise.AndroidDetechTouch;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class AndroidDetechTouchActivity extends Activity {
 
 TextView msg;
 TouchView touchView;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        msg = (TextView)findViewById(R.id.msg);
        touchView = (TouchView)findViewById(R.id.touchview);

    }

    public void updateMsg(String tMsg){
     msg.setText(tMsg);
    }
   
}

main.xml, to add the custom ImageView and a TextView overlapped.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />
 <FrameLayout 
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
     >
     <LinearLayout 
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
         android:orientation="vertical">
         <TextView
             android:id="@+id/msg"
             android:layout_width="fill_parent"
             android:layout_height="wrap_content"
             />
     </LinearLayout>
     <com.exercise.AndroidDetechTouch.TouchView
         android:id="@+id/touchview"
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
         android:background="@drawable/ic_launcher"
         />
 </FrameLayout>
</LinearLayout>

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