Start Camera auto-focusing, autoFocus()

To start auto-focusing for Android camera, simple call autoFocus() method of the camera object, and registers a callback function to run when the camera is focused. This method is only valid when preview is active (between startPreview() and before stopPreview()).



Callers should check getFocusMode() to determine if this method should be called. If the camera does not support auto-focus, it is a no-op and onAutoFocus(boolean, Camera) callback will be called immediately.

If your application should not be installed on devices without auto-focus, you must declare that your application uses auto-focus with the <uses-feature> manifest element.

If the current flash mode is not FLASH_MODE_OFF, flash may be fired during auto-focus, depending on the driver and camera hardware.

Continuous from last exercise "Save the camera image using MediaStore".

Modify control.xml, define id for the background of the layout. Such that we can start auto-focus when user click on the background.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:id="@+id/background"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   android:gravity="bottom"
   >
<Button
 android:id="@+id/takepicture" 
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text=" * Take Picture "
 android:layout_gravity="right"
 android:layout_margin="10px"
 />
</LinearLayout>

Modify AndroidCamera.java to call camera.autoFocus(myAutoFocusCallback), and register the AutoFocusCallback.

package com.exercise.AndroidCamera;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;

import android.app.Activity;
import android.content.ContentValues;
import android.content.pm.ActivityInfo;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.hardware.Camera.AutoFocusCallback;
import android.hardware.Camera.PictureCallback;
import android.hardware.Camera.ShutterCallback;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore.Images.Media;
import android.view.LayoutInflater;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;

public class AndroidCamera extends Activity implements SurfaceHolder.Callback{

 Camera camera;
 SurfaceView surfaceView;
 SurfaceHolder surfaceHolder;
 boolean previewing = false;
 LayoutInflater controlInflater = null;
 
 Button buttonTakePicture;
 
 final int RESULT_SAVEIMAGE = 0;
 
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
       setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
      
       getWindow().setFormat(PixelFormat.UNKNOWN);
       surfaceView = (SurfaceView)findViewById(R.id.camerapreview);
       surfaceHolder = surfaceView.getHolder();
       surfaceHolder.addCallback(this);
       surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
      
       controlInflater = LayoutInflater.from(getBaseContext());
       View viewControl = controlInflater.inflate(R.layout.control, null);
       LayoutParams layoutParamsControl
        = new LayoutParams(LayoutParams.FILL_PARENT,
        LayoutParams.FILL_PARENT);
       this.addContentView(viewControl, layoutParamsControl);
      
       buttonTakePicture = (Button)findViewById(R.id.takepicture);
       buttonTakePicture.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    camera.takePicture(myShutterCallback,
      myPictureCallback_RAW, myPictureCallback_JPG);
   }});
      
       LinearLayout layoutBackground = (LinearLayout)findViewById(R.id.background);
       layoutBackground.setOnClickListener(new LinearLayout.OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub

    buttonTakePicture.setEnabled(false);
    camera.autoFocus(myAutoFocusCallback);
   }});
   }
  
   AutoFocusCallback myAutoFocusCallback = new AutoFocusCallback(){

  @Override
  public void onAutoFocus(boolean arg0, Camera arg1) {
   // TODO Auto-generated method stub
   buttonTakePicture.setEnabled(true);
  }};
  
   ShutterCallback myShutterCallback = new ShutterCallback(){

  @Override
  public void onShutter() {
   // TODO Auto-generated method stub
   
  }};
  
 PictureCallback myPictureCallback_RAW = new PictureCallback(){

  @Override
  public void onPictureTaken(byte[] arg0, Camera arg1) {
   // TODO Auto-generated method stub
   
  }};
  
 PictureCallback myPictureCallback_JPG = new PictureCallback(){

  @Override
  public void onPictureTaken(byte[] arg0, Camera arg1) {
   // TODO Auto-generated method stub
   /*Bitmap bitmapPicture
    = BitmapFactory.decodeByteArray(arg0, 0, arg0.length); */
   
   Uri uriTarget = getContentResolver().insert(Media.EXTERNAL_CONTENT_URI, new ContentValues());

   OutputStream imageFileOS;
   try {
    imageFileOS = getContentResolver().openOutputStream(uriTarget);
    imageFileOS.write(arg0);
    imageFileOS.flush();
    imageFileOS.close();
    
    Toast.makeText(AndroidCamera.this,
      "Image saved: " + uriTarget.toString(),
      Toast.LENGTH_LONG).show();
    
   } catch (FileNotFoundException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }

   camera.startPreview();
  }};

 @Override
 public void surfaceChanged(SurfaceHolder holder, int format, int width,
   int height) {
  // TODO Auto-generated method stub
  if(previewing){
   camera.stopPreview();
   previewing = false;
  }
  
  if (camera != null){
   try {
    camera.setPreviewDisplay(surfaceHolder);
    camera.startPreview();
    previewing = true;
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }
 }

 @Override
 public void surfaceCreated(SurfaceHolder holder) {
  // TODO Auto-generated method stub
  camera = Camera.open();
 }

 @Override
 public void surfaceDestroyed(SurfaceHolder holder) {
  // TODO Auto-generated method stub
  camera.stopPreview();
  camera.release();
  camera = null;
  previewing = false;
 }
}

Download the files.

Related:
- Face detection for Camera