Application Not Opening

[stelios papamichael]

Hello there, i am a complete amateur as far as android application development goes but i have experience with java.I managed to build a flashlight application but when i run it it does not open and i do not know why that is,below i will post some of my scripts .java and .xml and i hope you can help figure it out.

NOTE : Android Studio was used

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="comspdesign.wixsite.httpsteliospapamichael0.flashlight">

<uses-permission android:name="android.permission.CAMERA"></uses-permission>
    <uses-feature android:name="android.hardware.camera"></uses-feature>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_flash"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

MainActivity.java

package comspdesign.wixsite.httpsteliospapamichael0.flashlight;

import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.media.Image;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageButton;

public class MainActivity extends AppCompatActivity {

    ImageButton imageButton;
    Camera camera;
    Camera.Parameters parameters;
    boolean isFlash = false;
    boolean isOn = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageButton = (ImageButton) findViewById(R.id.imageButton);

        // checking if the device has a flash available or not

        if(getApplicationContext().getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH))
        {
          camera =   camera.open(); // initialize camera
            parameters = camera.getParameters();
            isFlash = true;
        }

        imageButton.setOnClickListener(new View.OnClickListener() {
            @Override
                    public  void onClick(View v) {
                if(isFlash) { // if flash is available

                    if(!isOn) // but is not on
                    {
                        imageButton.setImageResource(R.drawable.on);
                        parameters.setFlashMode(Camera.Parameters.FLASH_MODE_ON); // turn it on
                        camera.setParameters(parameters);
                        camera.startPreview();
                        isOn = true;
                    }

                    else // already on
                    {
                        imageButton.setImageResource(R.drawable.on);
                        parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
                        camera.setParameters(parameters);
                        camera.stopPreview();
                        isOn = false;
                    }
                }

                else { // start an alert dialog if there is no flash available
                    AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                    builder.setTitle("Error");
                    builder.setMessage("Flash is not available on your device!");
                    builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.dismiss();
                            finish(); // finish activity
                        }
                    });

                    AlertDialog alertDialog = builder.create();
                    alertDialog.show();// displaying the alert dialog

                }

            }
        });

    }

    @Override
    protected void onStop() {
        super.onStop();
        // if the camera is still used by the app while the app has been closed, release it
        if(camera != null) {
            camera.release();
             camera = null;
        }
    }
}

MainActivity.xml

<?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:background="@color/background"
    tools:context="comspdesign.wixsite.httpsteliospapamichael0.flashlight.MainActivity">


    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Simple FlashLight"
        android:textSize="38dp"
        android:textColor="@color/colorPrimary"
        android:gravity="center"
        android:layout_marginTop="15dp"
        android:textStyle="bold"
        />

    <ImageButton
        android:layout_width="800px"
        android:layout_height="600px"
        android:src="@drawable/off"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:scaleType="fitCenter"
        android:background="@color/background"
        android:id="@+id/imageButton"
        />

</RelativeLayout>

Hope you can help me figure this one out!

[Brian Tkatch]

I'm no expert. Still learning myself!

When using Android Studio, though, you can see the logs. Also, using Log.d() to specify a tag, and then filter on that tag to see what is going on. You can check if you are making it to onCreate(), at the very least.

[stelios papamichael]

Brian Tkatch wrote:I'm no expert. Still learning myself!

When using Android Studio, though, you can see the logs. Also, using Log.d() to specify a tag, and then filter on that tag to see what is going on. You can check if you are making it to onCreate(), at the very least.

Ok, i fixed the issue that was causing the app to close but i came up to another problem that seems to crash the app again.Please check the post again since i will update the code files MainActivity.xml and MainActivity.java if you are willing to help me again ! Thanks in advance!

[stelios papamichael]

NVM, i cannot edit the post so here are the updated files :

.xml

<?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:background="@color/background"
    tools:context="comspdesign.wixsite.httpsteliospapamichael0.flashlight.MainActivity">


    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Simple FlashLight"
        android:textSize="38dp"
        android:textColor="@color/colorPrimary"
        android:gravity="center"
        android:layout_marginTop="15dp"
        android:textStyle="bold"
        />

    <ImageButton
        android:layout_width="800px"
        android:layout_height="600px"
        android:src="@drawable/off"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:scaleType="fitCenter"
        android:background="@color/background"
        android:id="@+id/imageButton"
        />

    <ImageButton
        android:layout_width="800px"
        android:layout_height="600px"
        android:src="@drawable/on"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:scaleType="fitCenter"
        android:background="@color/background"
        android:id="@+id/imageButton2"
        android:visibility="invisible"
        />

</RelativeLayout>

.java

package comspdesign.wixsite.httpsteliospapamichael0.flashlight;

import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.media.Image;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageButton;

public class MainActivity extends AppCompatActivity {

    ImageButton imageButton;
    Camera camera;
    Camera.Parameters parameters;
    boolean isFlash = false;
    boolean isOn = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageButton = (ImageButton) findViewById(R.id.imageButton);

        // checking if the device has a flash available or not

        if(getApplicationContext().getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH))
        {
          camera =   camera.open(); // initialize camera
            parameters = camera.getParameters();
            isFlash = true;
        }

        imageButton.setOnClickListener(new View.OnClickListener() {
            @Override
                    public  void onClick(View v) {
                if(isFlash) { // if flash is available

                    if(!isOn) // but is not on
                    {
                        //imageButton.setImageResource(R.drawable.on);
                        imageButton.findViewById(R.id.imageButton2).setVisibility(View.VISIBLE);
                        imageButton.findViewById(R.id.imageButton).setVisibility(View.INVISIBLE);
                        parameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH); // turn it on
                        camera.setParameters(parameters);
                        camera.startPreview();
                        isOn = true;
                    }

                    else // already on
                    {
                        imageButton.findViewById(R.id.imageButton2).setVisibility(View.INVISIBLE);
                        imageButton.findViewById(R.id.imageButton).setVisibility(View.VISIBLE);
                        parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
                        camera.setParameters(parameters);
                        camera.stopPreview();
                        isOn = false;
                    }
                }

                else { // start an alert dialog if there is no flash available
                    AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                    builder.setTitle("Error");
                    builder.setMessage("Flash is not available on your device!");
                    builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.dismiss();
                            finish(); // finish activity
                        }
                    });

                    AlertDialog alertDialog = builder.create();
                    alertDialog.show();// displaying the alert dialog

                }

            }
        });

    }

    @Override
    protected void onStop() {
        super.onStop();
        // if the camera is still used by the app while the app has been closed, release it
        if(camera != null) {
            camera.release();
             camera = null;
        }
    }
}

As you can see,i decided to play around with the images visibility instead of the resource of the image as that was causing my app to crash previously.But for some weird reason this setup does not seem to work even though it looks fine to me.I click on the off button when i launch the app and it crashes and the log files don't tell me much.Any ideas?Have i done something wrong in my code in general or in the order that my code is layed out?

[Tim Moores]

When using Android Studio, though, you can see the logs. Also, using Log.d() to specify a tag, and then filter on that tag to see what is going on. You can check if you are making it to onCreate(), at the very least.

This is good advice. Whenever an app crashes, there's a lot of important information in the log, foremost the stack trace that tells you what happened, and in which line of the code. Post the stack trace here.

[Dave Tolls]

Why aren't you using a ToggleButton?
That would get rid of the whole logic around visible/invisible and the isOn flag.
You could then also use onCheckedChange instead of onClick.

[stelios papamichael]

Dave Tolls wrote:Why aren't you using a ToggleButton?
That would get rid of the whole logic around visible/invisible and the isOn flag.
You could then also use onCheckedChange instead of onClick.

Any ideas on what i should change in my app to use a tohhlebutton or switch without re-writting the whole app?

[Dave Tolls]

Instead of having two ImageButtons you'd have a ToggleButton.
Instead of using onClick you'd use the onCheckChanged (I think that's the method) which gives you the View (ie ToggleButton) and the new value (on or off).

You can remove the isOn flag.
Inside the listener (now onChange) you'd not worry about the visible/invisible stuff (so throw that away) you'd just worry about the flash bit:

if (isFlash) {
    if (switchOn) {
        param.setFlashMode(on);
        camera.set etc
    } else {
        param.setFlashMode(off);
        camera.set etc
    }
} else {
    alert stuff
}

Note that that is not copy/paste code!

[stelios papamichael]

Dave Tolls wrote:Instead of having two ImageButtons you'd have a ToggleButton.
Instead of using onClick you'd use the onCheckChanged (I think that's the method) which gives you the View (ie ToggleButton) and the new value (on or off).

You can remove the isOn flag.
Inside the listener (now onChange) you'd not worry about the visible/invisible stuff (so throw that away) you'd just worry about the flash bit:

if (isFlash) {
    if (switchOn) {
        param.setFlashMode(on);
        camera.set etc
    } else {
        param.setFlashMode(off);
        camera.set etc
    }
} else {
    alert stuff
}

Note that that is not copy/paste code!

I read the documentation, show some other examples and tutorials on youtube about togglebuttons and switches but didn't find out if you can use images for this.As you saw i do wanna use my custom images and not just a pre-made toggle switch.

[Dave Tolls]

The accepted answer here pretty much covers it:
http://stackoverflow.com/questions/18598255/android-create-a-toggle-button-with-image-and-no-text

You're essentially creating a bespoke style for your toggles.
To me that's what you are trying to do, and shifting the heavy lifting into the XML definition of the style is preferable to carving out some code that is, basically, what the ToggleButton already does.

[stelios papamichael]

The only errors i get when running my app are these two but nowhere i could find a solution :

09-09 20:42:24.101 10348-10348/comspdesign.wixsite.httpsteliospapamichael0.flashlight E/Camera-JNI: android_hardware_Camera_native_setup Error: -1
09-09 20:42:24.101 10348-10348/comspdesign.wixsite.httpsteliospapamichael0.flashlight E/Camera: Camera new cameraInitNormal:-1

Any ideas?I tried a ton of things that i saw on youtube but could not find anything on google!