title: App keeps crashing, programmed in android studio
body: <pre><code>package kdev.circles;
  
  import android.support.v7.app.ActionBarActivity;
  import android.os.Bundle;
  import android.support.v7.app.AppCompatActivity;
  import android.view.Menu;
  import android.view.MenuItem;
  import android.view.View;
  import android.widget.Button;
  import android.widget.EditText;
  import android.widget.TextView;
  
  
  public class MainActivity extends AppCompatActivity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          final EditText ca = (EditText)findViewById(R.id.ca);
          final EditText cp = (EditText)findViewById(R.id.cp);
          final EditText sv = (EditText)findViewById(R.id.sv);
          final EditText r = (EditText)findViewById(R.id.radius);
          final TextView log = (TextView)findViewById(R.id.log);
          Button clear = (Button)findViewById(R.id.clear);
          Button solve = (Button)findViewById(R.id.Solve);
          clear.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View view) {
                  ca.setText("");
                  cp.setText("");
                  sv.setText("");
                  r.setText("");
              }
          });
          solve.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View view) {
                  if((r.toString()).equals("")) {
                      log.setText(log.getText() + "\n" + "error, no value entered");
                  }else{
                      sv.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText())) * Double.valueOf(String.valueOf(r.getText())) * Double.valueOf(String.valueOf(r.getText())) * 4 / 3 * 3.14159265));
                      cp.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText()))*3.14159265*2));
                      ca.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText()))*Double.valueOf(String.valueOf(r.getText()))*3.14159265));
                      log.setText(log.getText()+"\n"+"ca"+ca.getText()+"\n"+"sv"+sv.getText()+"\n"+"cp"+cp.getText());
                  }
              }
          });
  
  
      }
  
  
      @Override
      public boolean onCreateOptionsMenu(Menu menu) {
          // Inflate the menu; this adds items to the action bar if it is present.
          getMenuInflater().inflate(R.menu.menu_main, menu);
          return true;
      }
  
      @Override
      public boolean onOptionsItemSelected(MenuItem item) {
          // Handle action bar item clicks here. The action bar will
          // automatically handle clicks on the Home/Up button, so long
          // as you specify a parent activity in AndroidManifest.xml.
          int id = item.getItemId();
  
          //noinspection SimplifiableIfStatement
          if (id == R.id.action_settings) {
              return true;
          }
  
          return super.onOptionsItemSelected(item);
      }
  }
  </code></pre>
  
  <p>xml file:</p>
  
  <p></p>
  
  <pre><code>&lt;Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Solve"
      android:id="@+id/Solve"
      android:width="100dp"
      android:layout_alignParentBottom="true"
      android:layout_alignEnd="@+id/sv" /&gt;
  
  &lt;EditText
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:inputType="numberDecimal"
      android:ems="10"
      android:id="@+id/radius"
      android:layout_alignParentTop="true"
      android:layout_alignStart="@+id/editText" /&gt;
  
  &lt;EditText
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:inputType="numberDecimal"
      android:ems="10"
      android:id="@+id/editText"
      android:layout_alignParentTop="true"
      android:layout_alignParentEnd="true"
      android:layout_marginTop="49dp" /&gt;
  
  &lt;EditText
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:inputType="numberDecimal"
      android:ems="10"
      android:id="@+id/editText2"
      android:layout_below="@+id/editText"
      android:layout_alignStart="@+id/editText" /&gt;
  
  &lt;EditText
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:inputType="numberDecimal"
      android:ems="10"
      android:id="@+id/editText3"
      android:layout_below="@+id/editText2"
      android:layout_alignStart="@+id/editText2" /&gt;
  
  &lt;TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:textAppearance="?android:attr/textAppearanceLarge"
      android:text="circle&amp;apos;s perimeter"
      android:id="@+id/cp"
      android:layout_above="@+id/editText2"
      android:layout_alignParentStart="true" /&gt;
  
  &lt;TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:textAppearance="?android:attr/textAppearanceLarge"
      android:text="circle&amp;apos;s area"
      android:id="@+id/ca"
      android:layout_above="@+id/editText3"
      android:layout_alignParentStart="true" /&gt;
  
  &lt;TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:textAppearance="?android:attr/textAppearanceLarge"
      android:text="sphere&amp;apos;s volume"
      android:id="@+id/sv"
      android:layout_alignBottom="@+id/editText3"
      android:layout_alignParentStart="true" /&gt;
  
  &lt;TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:textAppearance="?android:attr/textAppearanceLarge"
      android:text="radius"
      android:id="@+id/textView3"
      android:layout_alignBottom="@+id/radius"
      android:layout_alignParentStart="true" /&gt;
  
  &lt;Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="clear"
      android:id="@+id/clear"
      android:layout_alignBottom="@+id/Solve"
      android:layout_alignStart="@+id/editText3" /&gt;
  
  &lt;TextView
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      android:textAppearance="?android:attr/textAppearanceLarge"
      android:text="Large Text"
      android:id="@+id/log"
      android:layout_below="@+id/editText3"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="57dp" /&gt;
  </code></pre>
  
  <p>
  Everything is working fine till i try opening it, i couldn't find the error, because my android virtual device wasn't connected to android studio properly. I am not sure what i should do. I did have another problem before but i realised that it was due to me using the findviewbyid function before the whole layout was loaded. I have solved that problem and tried a few different techniques to solve this problem but nothing worked.
  When i try and run the app it just crashes, i am not sure why?
  Any help will be usefull, thank you.
  this is the logcat:</p>
  
  <pre><code>12-10 15:21:18.030    1907-1907/kdev.circles W/art﹕ Verification of java.lang.CharSequence android.support.v7.widget.ResourcesWrapper.getQuantityText(int, int) took 123.881364ms
  12-10 15:21:18.520    1907-1907/kdev.circles D/AndroidRuntime﹕ Shutting down VM
  12-10 15:21:18.520    1907-1907/kdev.circles E/AndroidRuntime﹕ FATAL EXCEPTION: main
      Process: kdev.circles, PID: 1907
      java.lang.RuntimeException: Unable to start activity ComponentInfo{kdev.circles/kdev.circles.MainActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
              at android.app.ActivityThread.access$800(ActivityThread.java:135)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:136)
              at android.app.ActivityThread.main(ActivityThread.java:5017)
              at java.lang.reflect.Method.invoke(Native Method)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
       Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
              at kdev.circles.MainActivity.onCreate(MainActivity.java:21)
              at android.app.Activity.performCreate(Activity.java:5231)
              at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
              at android.app.ActivityThread.access$800(ActivityThread.java:135)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:136)
              at android.app.ActivityThread.main(ActivityThread.java:5017)
              at java.lang.reflect.Method.invoke(Native Method)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
  12-10 15:21:27.230    1907-1907/kdev.circles I/Process﹕ Sending signal. PID: 1907 SIG: 9
  12-10 15:21:31.360    2153-2153/kdev.circles D/AndroidRuntime﹕ Shutting down VM
  12-10 15:21:31.360    2153-2153/kdev.circles E/AndroidRuntime﹕ FATAL EXCEPTION: main
      Process: kdev.circles, PID: 2153
      java.lang.RuntimeException: Unable to start activity ComponentInfo{kdev.circles/kdev.circles.MainActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
              at android.app.ActivityThread.access$800(ActivityThread.java:135)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:136)
              at android.app.ActivityThread.main(ActivityThread.java:5017)
              at java.lang.reflect.Method.invoke(Native Method)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
       Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
              at kdev.circles.MainActivity.onCreate(MainActivity.java:21)
              at android.app.Activity.performCreate(Activity.java:5231)
              at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
              at android.app.ActivityThread.access$800(ActivityThread.java:135)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:136)
              at android.app.ActivityThread.main(ActivityThread.java:5017)
              at java.lang.reflect.Method.invoke(Native Method)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
  </code></pre>