Develop Reference

How to add autofocus to surface view?

I am working on a QR decoder app in which i have created a SurfaceView to display camera output and a ImageButton to select an image from gallery.
I am using google play services to decode the QR code which requires to use surface view to scan the QR using camera. But it is not focusing on its own.
Below is the code for the same.
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.util.SparseArray;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.ImageButton;
import android.widget.Toast;
import com.google.android.gms.vision.CameraSource;
import com.google.android.gms.vision.Detector;
import com.google.android.gms.vision.Frame;
import com.google.android.gms.vision.barcode.Barcode;
import com.google.android.gms.vision.barcode.BarcodeDetector;
public class Scanner extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_scanner);
final SurfaceView cameraView = (SurfaceView) findViewById(R.id.camera_view);
BarcodeDetector barcodeDectector = new BarcodeDetector.Builder(this).setBarcodeFormats(Barcode.QR_CODE).build();
final CameraSource cameraSource = new CameraSource.Builder(this,barcodeDectector).setRequestedPreviewSize(1920,1080).build();
cameraView.getHolder().addCallback(new SurfaceHolder.Callback() {
#Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
try {
cameraSource.start(cameraView.getHolder());
} catch (IOException e) {
e.printStackTrace();
}
}
#Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
}
#Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
cameraSource.stop();
}
});
barcodeDectector.setProcessor(new Detector.Processor<Barcode>() {
#Override
public void release() {
}
#Override
public void receiveDetections(Detector.Detections<Barcode> detections) {
final SparseArray<Barcode> barcodes = detections.getDetectedItems();
//QRcode found hence move to intent action.
if( barcodes.size() != 0){
Intent i = new Intent(Scanner.this,Verify.class);
i.putExtra("xml",barcodes.valueAt(0).displayValue);
startActivity(i);
}
}
});
ImageButton scanImage = (ImageButton) findViewById(R.id.scanImage);
scanImage.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//button action to be added
}
});
}
}
The activity_scanner.xml is as follows.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"">
<SurfaceView
android:layout_width="match_parent"
android:layout_height="400dip"
android:layout_weight="70"
android:id="#+id/camera_view"
android:layout_alignParentLeft="true"
/>
<ImageButton
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="#+id/scanImage"
android:layout_below="#+id/camera_view"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:src="#drawable/ic_image_black_48dp"
android:layout_alignRight="#+id/camera_view"
android:layout_alignEnd="#+id/camera_view" />
</RelativeLayout>

Try extending Surface view like this, and setFocusable(true).
public class CameraView extends SurfaceView implements SurfaceHolder.Callback {
public CameraView(Context context) {
super(context);
getHolder().addCallback(this);
setFocusable(true);
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
}
}
EDIT 1:
Then in layout you can use this class like this,
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://s...content-available-to-author-only...d.com/apk/res/android"
xmlns:tools="http://s...content-available-to-author-only...d.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">
<com.abhayjatindoshi.encryptorcode.qrlogin.javaclass.CameraView
android:layout_width="match_parent"
android:layout_height="400dip"
android:layout_weight="70"
android:id="#+id/camera_view"
android:layout_alignParentLeft="true"
/>
<ImageButton
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="#+id/scanImage"
android:layout_below="#+id/camera_view"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:src="#drawable/ic_image_black_48dp"
android:layout_alignRight="#+id/camera_view"
android:layout_alignEnd="#+id/camera_view" />
</RelativeLayout>
Use Layout like above.

try this:
cameraView.requestFocus();

cameraView.setFocusableInTouchMode(true);
cameraView.setFocusable(true);
cameraView.requestFocus();

Above did not solved mine "focus" problem but i come a cross other solution which helped me:
private void setCamFocusMode(){
if(null == mCamera) {
return;
}
/* Set Auto focus */
Parameters parameters = mCamera.getParameters();
List<String> focusModes = parameters.getSupportedFocusModes();
if(focusModes.contains(Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE)){
parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);
} else
if(focusModes.contains(Camera.Parameters.FOCUS_MODE_AUTO)){
parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
}
mCamera.setParameters(parameters);
}
oryginally posted here:
https://stackoverflow.com/a/27092999/6225516

If somebody still looking for this yet, I've solved it by adding .setAutoFocusEnabled(true) before .build, in the line:
BarcodeDetector barcodeDectector = new BarcodeDetector.Builder(this)
.setBarcodeFormats(Barcode.QR_CODE)
.build();*

Flash light app

i am making simple torch app by using switch button.On clicking switch button flash mode is on but it is not switching off.
my code:
package com.shibli.torch;
import android.os.Bundle;
import android.app.Activity;
import android.hardware.Camera.Parameters;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.Switch;
public class MainActivity extends Activity {
Switch s;
android.hardware.Camera cam;
Parameters params;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
s=(Switch) findViewById(R.id.switch1);
s.setOnCheckedChangeListener(new OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton arg0, boolean v) {
if( s.isChecked()){
try {
cam = android.hardware.Camera.open();
params = cam.getParameters();
} catch (RuntimeException e) {
}
finally{
params.setFlashMode(Parameters.FLASH_MODE_TORCH);
cam.setParameters(params);
cam.startPreview();
;
}}
else
{
params = cam.getParameters();
params.setFlashMode(Parameters.FLASH_MODE_OFF);
cam.setParameters(params);
cam.stopPreview();
}
}
});
}
}
xml layout:
<RelativeLayout 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:background="#000000" >
<Switch
android:id="#+id/switch1"
android:layout_width="fill_parent"
android:layout_height="45dp"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:gravity="center"
/>
</RelativeLayout>

First of all, the finaly() is not a good idea in that case, because if the cam failed to initialize, You will get a NullPointerException. Second, use the boolean value from the checkedChangeListener. I would do it similar to this way (not tested, but should point You to the right directiopn):
s.setOnCheckedChangeListener(new OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton arg0, boolean isChecked) {
if(isChecked==true){
try {
cam = android.hardware.Camera.open();
params = cam.getParameters();
params.setFlashMode(Parameters.FLASH_MODE_TORCH);
cam.setParameters(params);
cam.startPreview();
} catch (RuntimeException e) {
//Toast for the user, that it doesn´t work
}
}else{
if(cam!=null){
params = cam.getParameters();
params.setFlashMode(Parameters.FLASH_MODE_OFF);
cam.setParameters(params);
cam.stopPreview();
}
}

Android custom camera app retake often crashes

I am developing my own custom camera app,while running the application if I click the capture button my camera will capture the current position.what I actually need is retaking a photo whenever I need.But if I click the retake(take photo) button the app will crash.Here I attached my code below.So any one please help me to resolve the error.
MainActivity.java
package com.example.camera1;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.Toast;
public class MainActivity extends Activity {
private Camera cameraObject;
private ShowCamera showCamera;
private ImageView pic;
private Button takePhotoButton;
public static Camera isCameraAvailiable(){
Camera object = null;
try {
object = Camera.open();
}
catch (Exception e){
}
return object;
}
private PictureCallback capturedIt = new PictureCallback() {
#Override
public void onPictureTaken(byte[] data, Camera camera) {
Bitmap bitmap = BitmapFactory.decodeByteArray(data , 0, data .length);
if(bitmap==null){
Toast.makeText(getApplicationContext(), "not taken", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(getApplicationContext(), "taken", Toast.LENGTH_SHORT).show();
}
cameraObject.release();
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
takePhotoButton = (Button)findViewById(R.id.button_takephoto);
cameraObject = isCameraAvailiable();
showCamera = new ShowCamera(this, cameraObject);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(showCamera);
takePhotoButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
cameraObject = isCameraAvailiable();
cameraObject.stopPreview();
showCamera = new ShowCamera(getApplicationContext(), cameraObject);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(showCamera);
}
});
}
public void snapIt(View view){
cameraObject.takePicture(null, null, capturedIt);
}
#Override
public void onPause(){
super.onPause();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
ShowCamera.java
package com.example.camera1;
import java.io.IOException;
import android.content.Context;
import android.hardware.Camera;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class ShowCamera extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder holdMe;
private Camera theCamera;
public ShowCamera(Context context,Camera camera) {
super(context);
theCamera = camera;
holdMe = getHolder();
holdMe.addCallback(this);
}
#Override
public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
}
#Override
public void surfaceCreated(SurfaceHolder holder) {
try {
theCamera.setDisplayOrientation(90);
theCamera.setPreviewDisplay(holder);
theCamera.startPreview();
} catch (IOException e) {
}
}
#Override
public void surfaceDestroyed(SurfaceHolder arg0) {
theCamera.stopPreview();
}
}
activity_main.xml
<?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="horizontal" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="0.30"
android:orientation="vertical" >
<FrameLayout
android:id="#+id/camera_preview"
android:layout_width="fill_parent"
android:layout_height="350dp" />
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<Button
android:id="#+id/button_capture"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="snapIt"
android:text="#string/Capture" />
<Button
android:id="#+id/button_takephoto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/button_capture"
android:text="Take Photo" />
</RelativeLayout>
</LinearLayout>
</LinearLayout>

I think the reason is you called cameraObject.release(); in onPictureTaken. You can remove it. And, don't forget to call startPreview() again.
Because:
This method is only valid when preview is active (after
startPreview()). Preview will be stopped after the image is taken;
callers must call startPreview() again if they want to re-start
preview or take more pictures. This should not be called between
start() and stop().
After calling this method, you must not call startPreview() or take
another picture until the JPEG callback has returned.

cameraObject.release();
Remove this line from tour PictureCallback. Now you know reason your app crash is quite straight to me , you are not start camera and preview also after you capture image. Preview is something stop after you call PictureCallback ,you have resume it manually.
IF you dont want to manage this thing then i can advise you to use cwac-camera library which is simply awesome. All you need to do is extend your Fragment by CameraFragment and it will take your responsibility to manage this stuff .
Enjoy !

how to turn the flash on the phone (flashlight)?

There is a code that is to turn on the flash when you press the button, this is why it is not happening. Help me understand why this is not happening, please. Tested the application on samsung galaxy nexus and lg p970.
Activity:
package com.example.Flashlight;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.util.Log;
import android.view.View;
import android.widget.*;
public class MainActivity extends Activity {
Camera camera;
boolean isFlashOn;
boolean hasFlash;
Parameters params;
Button flashlightButton;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
checkFlashlight();
getCamera();
initFlashlightButton();
}
void checkFlashlight() {
hasFlash = getApplicationContext().getPackageManager()
.hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
if (!hasFlash) {
AlertDialog alert = new AlertDialog.Builder(
MainActivity.this).create(); alert.setTitle("Error");
alert.setMessage("Sorry, your device doesn't support flash light!");
alert.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
alert.show();
return;
}
}
// initialization button and click listener
private void initFlashlightButton() {
flashlightButton = (Button) findViewById(R.id.flash_light);
flashlightButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (isFlashOn) turnOffFlash();
else turnOnFlash();
}
});
}
private void getCamera() {
if (camera == null) {
try {
camera = Camera.open();
params = camera.getParameters();
} catch (RuntimeException e) {
Log.e("Camera Error. Failed to Open. Error: ", e.getMessage());
}
}
}
// here must be of the flash (it is not clear why this is not happening)
private void turnOnFlash() {
if (!isFlashOn) {
if (camera == null || params == null) return;
params = camera.getParameters();
params.setFlashMode(Parameters.FLASH_MODE_TORCH);
camera.setParameters(params);
camera.startPreview();
isFlashOn = true;
}
}
// flash OFF
private void turnOffFlash() {
if (isFlashOn) {
if (camera == null || params == null) return;
params = camera.getParameters();
params.setFlashMode(Parameters.FLASH_MODE_OFF);
camera.setParameters(params);
camera.stopPreview();
isFlashOn = false;
}
}
Layout:
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="match_parent" android:layout_width="match_parent">
<Button
android:id="#+id/flash_light"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Flashlight"/>
</RelativeLayout>
Manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.Flashlight"
android:versionCode="1"
android:versionName="1.0">
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-sdk android:minSdkVersion="8"/>
<application android:label="#string/app_name" android:icon="#drawable/ic_launcher">
<activity android:name=".MainActivity"
android:label="#string/app_name"
android:theme="#android:style/Theme.Black">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>

To turn on the Camera :
camera = Camera.open();
Parameters p = camera.getParameters();
p.setFlashMode(Parameters.FLASH_MODE_TORCH);
camera.setParameters(p);
camera.startPreview();
To turn off the Camera :
camera = Camera.open();
Parameters p = camera.getParameters();
p.setFlashMode(Parameters.FLASH_MODE_OFF);
camera.setParameters(p);
camera.stopPreview();
Also you'll need to put that in your manifest :
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />

Try adding this to your manifest:
<uses-feature android:name="android.hardware.camera.flash" />
<uses-permission android:name="android.permission.FLASHLIGHT" />

findViewById causing crash. Why?

I am trying to implement an activity which shows a camera preview and contains two buttons. Getting the camera preview is no problem but when I try findViewById for the button objects the app will crash. Not sure why that's happening.
package com.capstone.parking.nyc;
import java.io.IOException;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceView;
import android.view.SurfaceHolder;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.widget.Button;
import android.graphics.PixelFormat ;
import android.hardware.Camera;
import android.hardware.Sensor;
import android.hardware.SensorManager;
public class MainScreen extends Activity implements SurfaceHolder.Callback
{
Camera theCamera;
SurfaceView surfaceView;
SurfaceHolder surfaceHolder;
boolean preview = false;
private SensorManager mSensorManager;
private ShakeListener mSensorListener;
#Override
public void onCreate(Bundle savedInstanceState)
{
final Button TagBttn;
final Button ParkBttn;
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFormat(PixelFormat.UNKNOWN);
setContentView(R.layout.mainscreen);
/*
*
* This line causes the crash
*/
TagBttn = (Button) findViewById(R.id.tag);
// ParkBttn = (Button)findViewById(R.id.park);
surfaceView = (SurfaceView) findViewById(R.id.camera);
surfaceHolder = surfaceView.getHolder();
surfaceHolder.addCallback(this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
mSensorListener = new ShakeListener();
mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
mSensorManager.registerListener(mSensorListener,
mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
SensorManager.SENSOR_DELAY_UI);
Log.d("TAG", "onCreate MainScreen");
mSensorListener.setOnShakeListener(new ShakeListener.OnShakeListener()
{
public void onShake()
{
Log.d("SHAKE CHECK", "YUSSSSSS");
// if shaken, go to the search screen
startActivity(new Intent("com.capstone.parking.SEARCH"));
}
});
/* Tag.setOnClickListener(new OnClickListener()
{
public void onClick(View v)
{
/*
*
* ENTER TAG CODE HERE
*
*
Log.d("TAG", "tag button pressed");
}
});
/*
/* Park.setOnClickListener(new OnClickListener()
{
public void onClick(View v)
{
/*
*
* ENTER PARK CODE HERE
*
*
Log.e("TAG", "park button pressed");
}
});
*/
}
#Override
public void onResume()
{
super.onResume();
mSensorManager.registerListener(mSensorListener,
mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
SensorManager.SENSOR_DELAY_UI);
}
#Override
public void onStop()
{
mSensorManager.unregisterListener(mSensorListener);
super.onStop();
}
public void surfaceCreated(SurfaceHolder holder)
{
Log.e("TAG", "surfaceCreated");
theCamera = Camera.open();
try
{
theCamera.setPreviewDisplay(holder);
}
catch (IOException e)
{
Log.e("TAG", "surfaceCreated FAIL");
}
theCamera.startPreview();
preview = true;
}
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height)
{
Log.e("TAG", "surfaceChanged");
if(preview)
{
theCamera.stopPreview();
}
Camera.Parameters parameters = theCamera.getParameters();
parameters.setPreviewSize(width, height);
// parameters.set("orientation", "portrait");
// parameters.set("rotation", "90");
theCamera.setParameters(parameters);
theCamera.startPreview();
}
public void surfaceDestroyed(SurfaceHolder holder)
{
if(preview)
{
Log.e("TAG", "surfaceDestroyed");
theCamera.stopPreview();
theCamera.release();
theCamera = null;
preview = false;
}
}
}
If anyone could guide me in the right direction I would greatly appreciate it. Thanks!
mainscreen.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:background="#006699" >
<TextView
android:id="#+id/scroll"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="marquee"
android:focusable="true"
android:focusableInTouchMode="true"
android:marqueeRepeatLimit="marquee_forever"
android:scrollHorizontally="true"
android:singleLine="true"
android:text="#string/shake"
android:textColor="#ffff66"
android:textStyle="bold" />
<SurfaceView
android:id="#+id/camera"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="25dp"
android:layout_marginBottom="125dp"
android:layout_marginLeft="20dp"
android:layout_marginRight="20dp" >
</SurfaceView>
<ImageButton
android:id="#+id/tag"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_marginRight="25dp"
android:layout_marginBottom="50dp"
android:contentDescription="#string/desc"
android:background="#drawable/tagbuttonselect"
android:clickable="true" />
<ImageButton
android:id="#+id/park"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_marginLeft="25dp"
android:layout_marginBottom="50dp"
android:contentDescription="#string/desc"
android:background="#drawable/parkbuttonselect"
android:clickable="true" />
</RelativeLayout>
Edit**
Oh wow. I'm retarded. I just figured it out. I was using Button instead of ImageButton. SMH Sorry, guys. lol

Try changing TagBttn = (Button) findViewById(R.id.tag); to TagBttn = (ImageButton) findViewById(R.id.tag);

may be you are trying to find id is not in mainscreen.xml
here tag is an ImageButton no simole Button
try this
TagBttn = (ImageButton) findViewById(R.id.tag);

Your tag item is an ImageButton and you are casting it to a Button. Change it. ImageButton and Button are very different classes.

No matter how confusing it may sound, it turns out that ImageButton is not a subclass of Button. So you'd want to replace your code with:
final ImageButton TagBttn;
final ImageButton ParkBttn;
and then use:
TagBttn = (ImageButton) findViewById(R.id.tag);
ParkBttn = (ImageButton) findViewById(R.id.park);