Android: mi aplicación se bloquea cuando hay un campo editText en blanco

Tengo un problema con mi código. Sigue fallando cuando tengo un campo editText en blanco. Este bit de código está en la configuración de mi aplicación y funciona bien con los datos, pero cuando hay un campo en blanco se bloquea el programa. Aquí está el código para ello. No seas duro porque es mi primera aplicación de Android. Entonces, si alguien sabe cómo resolver el problema del campo de edición de texto en blanco, ¡sería muy apreciado! (Cualquier otro comentario sobre cómo mejorar la aplicación sería de gran ayuda).

Salu

package com.cleanyet.cyv100fp;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class sTasks extends Activity {


@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.tasks);     

    /*Sets Up the Variables*/
    Button done = (Button) findViewById(R.id.done1);
    EditText t1 = (EditText)findViewById(R.id.tbTask1);
    EditText t2 = (EditText)findViewById(R.id.tbTask2);
    EditText t3 = (EditText)findViewById(R.id.tbTask3);
    EditText t4 = (EditText)findViewById(R.id.tbTask4);
    EditText t5 = (EditText)findViewById(R.id.tbTask5);

    String FILENAME1 = "stask1";
    String FILENAME2 = "stask2";
    String FILENAME3 = "stask3";
    String FILENAME4 = "stask4";
    String FILENAME5 = "stask5";

    String task1 = null;
    String task2 = null;
    String task3 = null;
    String task4 = null;
    String task5 = null;

    String edit = "Edit Task";

    /*Fixes the Blank Field bug*/

    /*Sets up the file input*/
    FileInputStream fis = null;

    /*Gets the tasks set previously*/

    /*Task 1 set up*/
    try {
        fis = openFileInput(FILENAME1);
        byte[] dataArray = new byte[fis.available()];
        while (fis.read(dataArray) != -1){
            task1 = new String(dataArray);

        }

    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    finally {
        try {
            fis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    if (task1.toString().length() < 0) {

    task1.toString();

    t1.setText(task1);
    }
    else {
        t1.setText(edit);
    }
    /*Task 2 set up*/

    try {
        fis = openFileInput(FILENAME2);
        byte[] dataArray = new byte[fis.available()];
        while (fis.read(dataArray) != -1){
            task2 = new String(dataArray);

        }

    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    finally {
        try {
            fis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    if (task2.toString().length() < 0) {

    task2.toString();

    t2.setText(task2);
    }
    else {
        t2.setText(edit);
    }
    /*Task 3 set up*/

    try {
        fis = openFileInput(FILENAME3);
        byte[] dataArray = new byte[fis.available()];
        while (fis.read(dataArray) != -1){
            task3 = new String(dataArray);

        }

    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    finally {
        try {
            fis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    if (task3.toString().length() < 0) {

    task3.toString();

    t3.setText(task3);
    }
    else {
        t3.setText(edit);
    }
    /*Task 4 set up*/


    try {
        fis = openFileInput(FILENAME4);
        byte[] dataArray = new byte[fis.available()];
        while (fis.read(dataArray) != -1){
            task4 = new String(dataArray);

        }

    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    finally {
        try {
            fis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    if (task4.toString().length() < 0) {

    task4.toString();

    t4.setText(task4);
    }
    else {
        t4.setText(edit);
    }
    /*Task 5 set up*/           

    try {
        fis = openFileInput(FILENAME5);
        byte[] dataArray = new byte[fis.available()];
        while (fis.read(dataArray) != -1){
            task5 = new String(dataArray);

        }

    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    finally {
        try {
            fis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    if (task5.toString().length() < 0) {

    task5.toString();

    t5.setText(task5);
    }
    else {
        t5.setText(edit);
    }

    /*When changes have been made and done is clicked*/
    done.setOnClickListener(new View.OnClickListener() {

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

            /*Sets up the Variables*/
            EditText t1 = (EditText)findViewById(R.id.tbTask1);
            EditText t2 = (EditText)findViewById(R.id.tbTask2);
            EditText t3 = (EditText)findViewById(R.id.tbTask3);
            EditText t4 = (EditText)findViewById(R.id.tbTask4);
            EditText t5 = (EditText)findViewById(R.id.tbTask5);

            String tasks1 = t1.getText().toString();
            String tasks2 = t2.getText().toString();
            String tasks3 = t3.getText().toString();
            String tasks4 = t4.getText().toString();
            String tasks5 = t5.getText().toString();

            String FILENAME1 = "stask1";
            String FILENAME2 = "stask2";
            String FILENAME3 = "stask3";
            String FILENAME4 = "stask4";
            String FILENAME5 = "stask5";

            String task1 = tasks1;
            String task2 = tasks2;
            String task3 = tasks3;
            String task4 = tasks4;
            String task5 = tasks5;
            String edit = "Go to settings to make this task.";

            if (t1 != null){

                t1.setText(edit);
                /*t2.setText(edit);
                t3.setText(edit);
                t4.setText(edit);
                t5.setText(edit);*/

            };

            /*Put if statement here to catch the empty field*/

            /*Makes The Changes to the Tasks*/
            try {

                FileOutputStream fos1 = openFileOutput(FILENAME1, Context.MODE_PRIVATE);
                fos1.write(task1.getBytes());
                fos1.close();

            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            try {

                FileOutputStream fos2 = openFileOutput(FILENAME2, Context.MODE_PRIVATE);
                fos2.write(task2.getBytes());
                fos2.close();

            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            try {

                FileOutputStream fos3 = openFileOutput(FILENAME3, Context.MODE_PRIVATE);
                fos3.write(task3.getBytes());
                fos3.close();

            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            try {

                FileOutputStream fos4 = openFileOutput(FILENAME4, Context.MODE_PRIVATE);
                fos4.write(task4.getBytes());
                fos4.close();

            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            try {

                FileOutputStream fos5 = openFileOutput(FILENAME5, Context.MODE_PRIVATE);
                fos5.write(task5.getBytes());
                fos5.close();

            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }


            startActivity(new Intent("com.checkin.cyv100fp.settings"));

        }
    });

}



}