Detect Touch Event part IV - get touch area

Previous article: Detect Touch Event part III - get touch pressure and size

The method getTouchMajor() and getTouchMinor() (getTouchMajor(int pointerIndex) and getTouchMinor(int pointerIndex) for multi-touch) of MotionEvent returns the length of the major and minor axis of an ellipse that describes the touch area.

Example:

package com.TestSingleTouch;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.TextView;

public class TestSingleTouch extends Activity {
 
 public class TouchView extends View {
  
  private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
  private float x, y;
  private float touchMajor, touchMinor;
  boolean touching = false;
  
  float pressure = 0; //Touch pressure
  float size = 0;  //Touch size
  final static float PRESET_PRESSURE = 0xFF;
  final static float PRESET_SIZE = 300;
  
  public TouchView(Context context) {
   super(context);
   // TODO Auto-generated constructor stub 
  }
  
  @Override
  protected void onDraw(Canvas canvas) {
   // TODO Auto-generated method stub
   if(touching){
    
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setStrokeWidth(1);
    
    paint.setColor(Color.WHITE);
    RectF ovalTouch = new RectF(x-touchMajor/2, y-touchMinor/2, x+touchMajor/2, y+touchMinor/2);

    canvas.drawOval(ovalTouch, paint);
   } 
  }
  
  @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
   
   pressure = event.getPressure();
   if(pressure > 1){
    pressure = 1; 
   }

   size =event.getSize();
   
   String act;
   
   int action = event.getAction();
   
   switch(action){
   case MotionEvent.ACTION_MOVE:
    act = "ACTION_MOVE\n";
    x = event.getX();
    y = event.getY();
    touchMajor = event.getTouchMajor();
    touchMinor = event.getTouchMinor();
    touching = true;
    break; 
   case MotionEvent.ACTION_DOWN:
    act = "ACTION_DOWN\n";
    x = event.getX();
    y = event.getY();
    touchMajor = event.getTouchMajor();
    touchMinor = event.getTouchMinor();
    touching = true;
    break;
   case MotionEvent.ACTION_UP:
    act = "ACTION_UP\n";
    touching = false;
    break; 
   default:
    act = "XXX\n";
    touching = false; 
   }
   
   act += event.toString();
   textView.setText(act);
   
   invalidate();
   return true; 
  } 
 }
 
 TextView textView;
 
 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  //setContentView(new TouchView(this));
  textView = new TextView(this);
  textView.setText("Waiting");
  TouchView touchView = new TouchView(this);
  LinearLayout mainScreen = new LinearLayout(this);
  mainScreen.setOrientation(LinearLayout.VERTICAL);
  mainScreen.addView(textView);
  mainScreen.addView(touchView);
  setContentView(mainScreen); 
 }
}

Tweet