App hangs after ending loop in Thread

Question

Hello, I made an app in Android Studio that breaks the phrases in words and stores in an array using split. Then I made a loop of repetition using while so that it displays word for word, but there was a problem, the application would freeze the screen, and after having done the whole loop would update it and only appeared the last word of the vector. To solve this I used a Thread, solved, it updates, but the app hangs when it ends. Can someone help me?

Code:

button.setOnClickListener(
                new View.OnClickListener(){
                    public void onClick(View view){
                        Thread t1 = new Thread(){
                            int wpm;
                            String frase;
                            int numbers;
                            int i;
                            @Override
                            public void run(){
                                numbers = Integer.parseInt(txt2.getText().toString());
                                wpm = 1000/(numbers/60);
                                frase = txt1.getText().toString();
                                final String palavras[] = frase.split(" ");
                                i = 0;
                                while(i++ < palavras.length){
                                    try {
                                        runOnUiThread(new Runnable() {
                                            @Override
                                            public void run() {
                                                label.setText(String.valueOf(palavras[i]));
                                            }
                                        });
                                        Thread.sleep(wpm);
                                    } catch (InterruptedException e) {
                                        e.printStackTrace();
                                    }
                                }
                            }
                        };
                        t1.start();
                    }
                }
        );

Logcat:

05-02 01:33:16.142 6738-6738/com.exsapps.readfast E/Androidruntime: FATAL EXCEPTION: main Process: com.exsapps.readfast, PID: 6738 java.lang.Arrayindexoutofboundsexception: length=122; index=122 at.exsapps.readfast.Main$1$1$1.run(Main.java:48) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.Activitythread.main(Activitythread.java:7409) at java.lang.reflect.Method.invoke(Native Method) at com.android.Internal.os.Zygoteinit$Methodandargscaller.run(Zygoteinit.java:1230) at com.android.Internal.os.Zygoteinit.main(Zygoteinit.java:1120)

Answer 1

I read Carlos' comment, and tried and went wrong, after that I added the loop control variable to be declared at the beginning of the code and in the loop I used only for(i = 0; i < words.length; i++){} and the problem was solved, the application runs, and after its execution, it does not lock.

Code:

    public class Main extends AppCompatActivity {
    Button button;
    EditText txt1;
    EditText txt2;
    TextView label;
    public int i; // < -- Essa foi a solução
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button)findViewById(R.id.button);
        label = (TextView)findViewById(R.id.label);
        txt1 = (EditText)findViewById(R.id.txt1);
        txt2 = (EditText)findViewById(R.id.txt2);
        button.setOnClickListener(
                new View.OnClickListener(){
                    public void onClick(View view){
                        Thread t1 = new Thread(){
                            int wpm;
                            String frase;
                            int numbers;
                            @Override
                            public void run(){
                                numbers = Integer.parseInt(txt2.getText().toString());
                                wpm = 1000/(numbers/60);
                                frase = txt1.getText().toString();
                                final String palavras[] = frase.split(" ");
                                for(i = 0; i < palavras.length; i++){
                                    try {
                                        runOnUiThread(new Runnable() {
                                            @Override
                                            public void run(){

  label.setText(String.valueOf(palavras[i]));
                                            }
                                        });
                                        Thread.sleep(wpm);
                                    } catch (InterruptedException e) {
                                        e.printStackTrace();
                                    }
                                }
                            }
                        };
                        t1.start();
                    }
                }
        );
    }

}

Answer 2

The problem must be while(i++ < palavras.length) that is, i is being compared and afterward then within the loop the final value of i will end up being palavras.length which is an invalid entry.

I advise using a for as in (very conventional, every programmer will recognize):

for (int i = 0; i < palavras.length; i++) {
    final String palavra = palavras[i];
    ...
        label.setText(palavra);
    ...
}