Gestures detection and canvas scale, translate and rotate.

Further works on previous SurfaceView Game step-by-step: react device movement/orientation using accelerometer; in this article we are going to implement GestureOverlayView to detect gestures input, and apply scale, translate and rotate on canvas accordingly.

- In order to make it simple, disable Sensor function, comment the myAccelerometer related code in MyGameActivity.java.

- Create gestures of up/down/left/right, clockwise/anti-clockwise, enlarge/reduce, refer to the article Gestures Builder: create your gestures library. And copy the generated file to /res/raw folder.
(May be I build the Gestures too simple, the detection is not accurate. You are advised to create your own.)

- Modify main.xml to add android.gesture.GestureOverlayView.

<?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"
  >

<com.MyGame.MyGameSurfaceView
  android:id="@+id/myview1"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent" />
<com.MyGame.MyForeground
  android:id="@+id/myforeground"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent" />

 <android.gesture.GestureOverlayView
     android:id="@+id/gestures"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:gestureStrokeType="multiple"
     android:eventsInterceptionEnabled="true"/>

</FrameLayout>
</LinearLayout>

- Modify MyGameActivity.java to handle Gesture.

package com.MyGame;

import java.util.ArrayList;

import android.app.Activity;
import android.gesture.Gesture;
import android.gesture.GestureLibraries;
import android.gesture.GestureLibrary;
import android.gesture.GestureOverlayView;
import android.gesture.GestureOverlayView.OnGesturePerformedListener;
import android.gesture.Prediction;
import android.graphics.PixelFormat;
import android.os.Bundle;
import android.view.SurfaceView;
import android.widget.Toast;

public class MyGameActivity extends Activity {
 
 MyGameSurfaceView myGameSurfaceView1;
 MyForeground myForeground;
 
 //MyAccelerometer myAccelerometer;
 
 GestureLibrary gestureLibrary = null;
 GestureOverlayView gestureOverlayView;
 
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  myGameSurfaceView1 = (MyGameSurfaceView)findViewById(R.id.myview1);
  myForeground = (MyForeground)findViewById(R.id.myforeground);

  //Set myForeground using transparent background
  myForeground.setZOrderOnTop(true);
  myForeground.getHolder().setFormat(PixelFormat.TRANSPARENT);

  //myAccelerometer = new MyAccelerometer(this);

  gestureOverlayView = (GestureOverlayView)findViewById(R.id.gestures);
  gestureLibrary = GestureLibraries.fromRawResource(this, R.raw.gestures);
  gestureLibrary.load();
  gestureOverlayView.addOnGesturePerformedListener(gesturePerformedListener);

}

OnGesturePerformedListener gesturePerformedListener
= new OnGesturePerformedListener(){

  @Override
  public void onGesturePerformed(GestureOverlayView view, Gesture gesture) {
   ArrayList<Prediction> prediction = gestureLibrary.recognize(gesture);
   
     if(prediction.size() > 0){
      String gesturePerformed = prediction.get(0).name;
      if(gesturePerformed.equals("up")){
       myForeground.canvasUp();
       Toast.makeText(MyGameActivity.this,
         "up", Toast.LENGTH_LONG).show();
      }else if(gesturePerformed.equals("down")){
       myForeground.canvasDown();
       Toast.makeText(MyGameActivity.this,
         "down", Toast.LENGTH_LONG).show();
      }else if(gesturePerformed.equals("left")){
       myForeground.canvasLeft();
       Toast.makeText(MyGameActivity.this,
         "left", Toast.LENGTH_LONG).show();
      }else if(gesturePerformed.equals("right")){
       myForeground.canvasRight();
       Toast.makeText(MyGameActivity.this,
         "right", Toast.LENGTH_LONG).show();
      }else if(gesturePerformed.equals("clockwise")){
       myForeground.canvasClockwise();
       Toast.makeText(MyGameActivity.this,
         "clockwise", Toast.LENGTH_LONG).show();
      }else if(gesturePerformed.equals("anti-clockwise")){
       myForeground.canvasAntiClockwise();
       Toast.makeText(MyGameActivity.this,
         "anti-clockwise", Toast.LENGTH_LONG).show();
      }else if(gesturePerformed.equals("enlarge")){
       myForeground.canvasEnlarge();
       Toast.makeText(MyGameActivity.this,
         "enlarge", Toast.LENGTH_LONG).show();
      }else if(gesturePerformed.equals("reduce")){
       myForeground.canvasReduce();
       Toast.makeText(MyGameActivity.this,
         "reduce", Toast.LENGTH_LONG).show();
      }
     }
   
  }
 
};

 @Override
 protected void onResume() {
  // TODO Auto-generated method stub
  super.onResume();
  myGameSurfaceView1.MyGameSurfaceView_OnResume();
  myForeground.MyGameSurfaceView_OnResume();
  
  //myAccelerometer.registerListener();

 }

 @Override
 protected void onPause() {
  // TODO Auto-generated method stub
  super.onPause();
  myGameSurfaceView1.MyGameSurfaceView_OnPause();
  myForeground.MyGameSurfaceView_OnPause();
  
  //myAccelerometer.unregisterListener();
 }
 
 void updateAccelerometer(float tx, float ty){
  int w = myForeground.getWidth();
  int h = myForeground.getHeight();
  
  float x = ((w/2) * tx) + (w/2);
  float y = ((h/2) * ty) + (h/2);
  myForeground.updateAccelerometer(x, y);
 }

}

- Modify MyForeground.java to handle canvas scale, translate and rotate.

package com.MyGame;

import android.content.Context;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.PorterDuff.Mode;
import android.util.AttributeSet;

public class MyForeground extends MyGameSurfaceView {
 
 Sprite mySprite;
 
 float canvasScaleX = 1.0f;
 float canvasScaleY = 1.0f;
 float canvasTranslateX = 0.0f;
 float canvasTranslateY = 0.0f;
 float canvasRotate = 0.0f;

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

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

 public MyForeground(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  init();
 }
 
 private void init(){
  mySprite = new Sprite(
    BitmapFactory.decodeResource(getResources(), R.drawable.icon_me),
    100, 100);
 }

 @Override
 protected void onDraw(Canvas canvas) {
  //Clear Canvas with transparent background
  canvas.drawColor(Color.TRANSPARENT, Mode.CLEAR);
  
  canvas.scale(canvasScaleX, canvasScaleY);
  canvas.translate(canvasTranslateX, canvasTranslateY);
  canvas.rotate(canvasRotate, mySprite.getX(), mySprite.getY());
  mySprite.draw(canvas);
  
 }

 @Override
 public void updateStates() {
  // TODO Auto-generated method stub
  mySprite.update();
 }
 
 void updateAccelerometer(float tx, float ty){
  mySprite.setX((int)tx);
  mySprite.setY((int)ty);
 }
 
 public void canvasUp(){
  canvasTranslateY -= 10.0f;
 }
 
 public void canvasDown(){
  canvasTranslateY += 10.0f;
 }
 
 public void canvasLeft(){
  canvasTranslateX -= 10.0f;
 }
 
 public void canvasRight(){
  canvasTranslateX += 10.0f;
 }
 
 public void canvasClockwise(){
  canvasRotate += 10.0f;
 }
 
 public void canvasAntiClockwise(){
  canvasRotate -= 10.0f;
 }
 
 public void canvasEnlarge(){
  canvasScaleX *= 2.0f;
  canvasScaleY *= 2.0f;
 }
 
 public void canvasReduce(){
  canvasScaleX /= 2.0f;
  canvasScaleY /= 2.0f;
 }

}