Android App Keeps Crashing on Startup

Question

Android application keeps crashing on start-up. Everything appears fine to me, though.

Stack trace:

01-24 21:23:41.417: I/Process(767): Sending signal. PID: 767 SIG: 9
01-24 21:41:36.316: W/Trace(890): Unexpected value from nativeGetEnabledTags: 0
01-24 21:41:36.485: W/Trace(890): Unexpected value from nativeGetEnabledTags: 0
01-24 21:41:36.515: W/Trace(890): Unexpected value from nativeGetEnabledTags: 0
01-24 21:41:36.515: D/dalvikvm(890): newInstance failed: p0 i0 [0 a1
01-24 21:41:36.515: D/AndroidRuntime(890): Shutting down VM
01-24 21:41:36.515: W/dalvikvm(890): threadid=1: thread exiting with uncaught     exception (group=0x40a70930)
01-24 21:41:36.635: E/AndroidRuntime(890): FATAL EXCEPTION: main
01-24 21:41:36.635: E/AndroidRuntime(890): java.lang.RuntimeException: Unable to     instantiate activity ComponentInfo{com.example.bmisummative/com.example.bmisummative.MainActivity}:     java.lang.InstantiationException: can't instantiate class     com.example.bmisummative.MainActivity
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.os.Looper.loop(Looper.java:137)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.main(ActivityThread.java:5039)
01-24 21:41:36.635: E/AndroidRuntime(890):  at java.lang.reflect.Method.invokeNative(Native Method)
01-24 21:41:36.635: E/AndroidRuntime(890):  at java.lang.reflect.Method.invoke(Method.java:511)
01-24 21:41:36.635: E/AndroidRuntime(890):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-24 21:41:36.635: E/AndroidRuntime(890):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-24 21:41:36.635: E/AndroidRuntime(890):  at dalvik.system.NativeStart.main(Native Method)
01-24 21:41:36.635: E/AndroidRuntime(890): Caused by: java.lang.InstantiationException: can't instantiate class com.example.bmisummative.MainActivity
01-24 21:41:36.635: E/AndroidRuntime(890):  at java.lang.Class.newInstanceImpl(Native Method)
01-24 21:41:36.635: E/AndroidRuntime(890):  at java.lang.Class.newInstance(Class.java:1319)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
01-24 21:41:36.635: E/AndroidRuntime(890):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
01-24 21:41:36.635: E/AndroidRuntime(890):  ... 11 more
01-24 21:46:36.745: I/Process(890): Sending signal. PID: 890 SIG: 9

MainActivity class:

package com.example.bmisummative;

import android.app.Activity;
import android.content.DialogInterface;
import android.view.View.OnClickListener;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public abstract class MainActivity extends Activity implements OnClickListener {
/** Called when the activity is first created. */
Button btn,btn1,btn2;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btn = (Button) findViewById(R.id.buttonBMI);
    btn.setOnClickListener(this);
    btn1 = (Button) findViewById(R.id.buttonGain);
    btn1.setOnClickListener(this);
    btn2 = (Button) findViewById(R.id.buttonLoss);
    btn2.setOnClickListener(this);

}

@Override
public void onClick(View v) {
  if (v.getId() == R.id.buttonBMI) {
    startActivity(new Intent(this, MainActivity.class));
  }
  if (v.getId() == R.id.buttonGain) {
    startActivity(new Intent(this, weightgain.class));
  }
  if (v.getId() == R.id.buttonLoss) {
        startActivity(new Intent(this, weightgain.class));
      }

}

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    tools:context=".StartingPoint" 
    android:background="@drawable/grunge">

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Main Menu"
        android:textSize="45dp"
        android:layout_gravity="center"
        android:gravity="center" 
        android:textColor="#FFFFFF"
        android:id="@+id/tvDisplay"/>

    <Button
        android:id="@+id/buttonBMI"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="BMI Calculator"
        android:textSize="20dp" />

    <Button
        android:id="@+id/buttonLoss"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="Weight Loss Workouts"
        android:textSize="20dp" />

    <Button
        android:id="@+id/buttonGain"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="Muscle Gain Workouts"
        android:textSize="20dp" />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.bmisummative"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.bmisummative.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.example.bmiworking.calculator"
            android:label="@string/app_name" >
            </activity>

            <activity
            android:name="com.example.bmiworking.weightgain"
            android:label="@string/app_name" >
            </activity>
            <activity
            android:name="com.example.bmiworking.weightloss"
            android:label="@string/app_name" >
            </activity>
            </application> 
</manifest>

Answer 1

When you are declaring your activities in the manifest, try removing the package before the activity name, so you get android:name=".MainActivity" and do the same with your other activities.

Okay my first answer was wrong. The reason that your app is crashing is because you have declared your main activity as abstract delete this and your app should run.

Answer 2

Your activity should not be abstract.

You should also get used to wrapping your functions in at least

try {
   /// Do some work
} catch (Throwable t) {
   Log.e(TAG, t.getMessage(), t);
}

In my activity classes I define TAG as:

public static final String TAG = "NameMeSomethingUnique";

Changing the value of the string to generally the name of the activity.

EDIT

Rather than showing your entire class rewritten. I'm just modifying the onCreate for the try/catch and adding the TAG constant as a class member. You can add the try/catch blocks to the other methods in the same way.

public class MainActivity extends Activity implements OnClickListener { // REMOVED abstract keyword - EJN
/** Called when the activity is first created. */
Button btn,btn1,btn2;
private static final String TAG = "MainActivity"; // Used to make logging easier - EJN

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    try { // Wrapped to trap any possible exceptions so we don't just crash - EJN
        setContentView(R.layout.activity_main);
        btn = (Button) findViewById(R.id.buttonBMI);
        btn.setOnClickListener(this);
        btn1 = (Button) findViewById(R.id.buttonGain);
        btn1.setOnClickListener(this);
        btn2 = (Button) findViewById(R.id.buttonLoss);
        btn2.setOnClickListener(this);
    } catch (Throwable t) {
        Log.e(TAG, t.getMessage(), t);
    }
}