EditText.getText().toString() crashes

In my android application , I have 3 dialogue boxes in which the user puts info into 3 editTexts and it will display the one of the data onto another class/page after it randomly picks which data to choose.

This is my mainClass

public class MainActivity extends Activity {
   //Variables are displayed in this area 
    String choices[] = new String[3];
    //EditText editText;
    //EditText editText2;
    //EditText editText3;
    Button mainButton ; 

    Random rand = new Random(); 
    int finalChoice; 
    String displayChoice = ""; 
    EditText editText ; 
    EditText editText2; 
    EditText editText3;
    EditText editText4; 
    String test;
    int count = 3; 


//--------------------------- --------------------------------------------------------


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        //Makes Button

        setContentView(R.layout.activity_main);
        declareTextBox(); 
        setButton(); 
        String choice1 = editText.getText().toString();
        String choice2 = editText2.getText().toString(); 
        String choice3 = editText3.getText().toString();

        choices[0] = choice1; //pass from click button to method.
        choices[1] = choice2;
        choices[2] = choice3;  

        finalChoice =rand.nextInt(2);


    }
     public void setButton()
     {
         final Button mainbutton = (Button) findViewById(R.id.mainButton);

         mainbutton.setOnClickListener(new View.OnClickListener() {
         public void onClick(View v) {

             test =  ((EditText) findViewById(R.id.editText4)).getText().toString(); 

        // count++; 
         //retChoice(); 
            // loadScreen(); 
         Intent i  = new Intent(MainActivity.this, resultScreen.class);
         i.putExtra("display" , displayChoice);

         Intent intent = new Intent(MainActivity.this,loadingScreen.class);

            //start the second Activity
         MainActivity.this.startActivity(intent);


          }
      }); 

     }
    public void declareTextBox()
    {
        editText = (EditText) findViewById(R.id.editText1);
        editText2 =  (EditText) findViewById(R.id.editText2); 
        editText3 = (EditText) findViewById(R.id.editText3); 

    }
    public void getString(String finalChoice)
    {
        finalChoice = displayChoice; 
    }


    public String retChoice()
    {


        displayChoice = choices[finalChoice];

        return displayChoice; 
    }
    public void clearText()
    {
         editText.setOnClickListener(new View.OnClickListener() {

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

                 editText.setText(" "); 
                }
            }); 

         editText2.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    editText2.setText(" "); 
                }
            }); 

         editText3.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    editText3.setText(" "); 
                }
            }); 

    }
    public void getText2()
    {

    }
    public void 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.main, menu);
        return true;
    }
}

This is my Display class :

public class resultScreen extends Activity {
    MainActivity ma = new MainActivity(); 
    //Method supposedly retrieves the string data from MainActivity Class but somehow displayed null instead. 
    //Find a way to keep the string variable when transfering from one class to another class. 
      String finalResult = ma.retChoice(); 
      public void onCreate(Bundle resultScreen){
      super.onCreate(resultScreen);
      setContentView(R.layout.resultscreen);
      //ma.displayChoice.toString(); 

      String str = finalResult;

      TextView text = (TextView) findViewById(R.id.textView1);
      text.setText(str);

      final Button backbutton = (Button) findViewById(R.id.backButton);
      backbutton.setOnClickListener(new View.OnClickListener() {
      public void onClick(View v) 

      {

      Intent intent = new Intent(resultScreen.this,MainActivity.class);
      resultScreen.this.startActivity(intent);     


      }
        });



        }

}

And this is my loading screen class right after the main button is clicked

public class loadingScreen extends Activity{

protected void onCreate(Bundle loadingScreen) {
    // TODO Auto-generated method stub

    super.onCreate(loadingScreen);
    setContentView(R.layout.loadingscreen);


    //If sound clip 20 sec long we don't want to carryit outside next class


    // A timer thread looking for "run" method
    Thread timer = new Thread()
    {
        public void run() {
            try {

                //this is how many mil sec
                sleep(8000);


            } catch (InterruptedException e) {
                e.printStackTrace();

            } finally {
                Intent intent = new Intent(loadingScreen.this, resultScreen.class);
                loadingScreen.this.startActivity(intent);
                loadingScreen.this.finish();

             }

        }
    };
    timer.start();
}

}

My app crashes a few seconds into the loading screen when the program attempts to display the data on the resultScreen.

Here's my logCat

    05-17 22:32:54.446: D/AndroidRuntime(1181): Shutting down VM
05-17 22:32:54.446: W/dalvikvm(1181): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
05-17 22:32:54.636: E/AndroidRuntime(1181): FATAL EXCEPTION: main
05-17 22:32:54.636: E/AndroidRuntime(1181): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.choiceprototest/com.example.choiceprototest.resultScreen}: java.lang.NullPointerException
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.os.Looper.loop(Looper.java:137)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.app.ActivityThread.main(ActivityThread.java:5039)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at java.lang.reflect.Method.invokeNative(Native Method)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at java.lang.reflect.Method.invoke(Method.java:511)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at dalvik.system.NativeStart.main(Native Method)
05-17 22:32:54.636: E/AndroidRuntime(1181): Caused by: java.lang.NullPointerException
05-17 22:32:54.636: E/AndroidRuntime(1181):     at com.example.choiceprototest.MainActivity.retChoice(MainActivity.java:101)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at com.example.choiceprototest.resultScreen.<init>(resultScreen.java:18)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at java.lang.Class.newInstanceImpl(Native Method)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at java.lang.Class.newInstance(Class.java:1319)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
05-17 22:32:54.636: E/AndroidRuntime(1181):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
05-17 22:32:54.636: E/AndroidRuntime(1181):     ... 11 more
05-17 22:33:03.385: I/Process(1181): Sending signal. PID: 1181 SIG: 9
05-17 22:33:05.435: E/Trace(1204): error opening trace file: No such file or directory (2)

Thanks guys.

回答1:

I believe I see the problem. You are trying to access your Array but it is an instance variable instead of static so it is being killed off when you exit your Activity. You can either put them in a static class and access them that way or pass a String variable through your Intent, depending on what you need.

If you have the value of the String you need when you leave MainActivity then I would probably just pass it through your Intent. If the value depended on something in one of your other Activities then I would consider putting it in a separate class but it doesn't look like that's what you need here

Edit

You are already doing it here, kind of

Intent i  = new Intent(MainActivity.this, resultScreen.class);
     i.putExtra("display" , displayChoice);

     Intent intent = new Intent(MainActivity.this,loadingScreen.class);

But you aren't starting the Activity that would get the String

i.putExtra("display" , displayChoice);

that line would pass a String with key "displpay" and value of displayChoice, although I think that value is an empty String at that point, but you don't start that Activity. I'm lost on how your flow is suppose to work but basically you would do something like this

String displayChoice = "testValue";   // some arbitrary value--whatever you need to send
Intent i  = new Intent(MainActivity.this, resultScreen.class);  // create the Intent
i.putExtra("display" , displayChoice);  // add the extra
startActivity(i);  //start the Activity

then to get the value inside resultScreen in onCreate()

Intent recIntent = getIntent();  // get the Intent that started this Activity
String value = recIntent.getStringExtra("display");   // get the value using the key
// value now equals "testValue"

回答2:

I think your app chash because you have an ANR: "Application Not Responding" because you are running a long procces inside the UIThread. (onCreate() method is form the UIThread)

Use rather as an Asyntack for your sleeping thread or one handler (with messages).

If you need more I can edit your code tomorrow.