在 Android Studio 中单击按钮时，onClickListener 使应用程序崩溃

Question

I am trying to make an application in which the word Sorry. will print as much time as the input given by user button as soon as the button is clicked the crashes, Even if I try set a Toast in onclicklistener, the app doesn't crash. but toast is not formed. I think there is some problem in the Java file: Here's the java file:

    package com.example.satvara.vipul.instantmessage;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class Sorry extends AppCompatActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sorry);
        this.setTitle(R.string.activity_sorry);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        EditText editText= findViewById(R.id.editText);
        String str = editText.getText().toString();
        final int i= Integer.parseInt(str);
        final TextView textView=findViewById(R.id.textView);
        Button btn=findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                for (int j=0; j>i;j++){
                    textView.setText("Sorry!");
                }
            }
        });

    }

}

Here's the XML file:

    <?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Sorry">
    <TableLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TableRow>
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Number:"
                android:padding="10dp"
                android:textSize="20dp"
                android:textColor="@color/text"
                android:layout_column="1"/>
            <EditText
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:hint="Enter Here"
                android:paddingLeft="7dp"
                android:paddingRight="7dp"
                android:backgroundTint="@color/colorPrimaryDark"
                android:textCursorDrawable="@drawable/cursor_color"
                android:inputType="number"
                android:id="@+id/editText"/>
        </TableRow>
        <TableRow>
            <Button
                android:layout_column="2"
                android:hint="Send via Whatsapp"
                android:id="@+id/btn"
                ></Button>
        </TableRow>
        <TableRow>
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/textView">
            </TextView>
        </TableRow>
    </TableLayout>

</android.support.constraint.ConstraintLayout>

Answer 1

You have to put get edit text in onClick(). Your for loop condition is wrong. Even if it was correct you were just setting the same text for i times. You should only use the loop for setting the value of the yourString and later when the loop is over setText(yourString)

public class Sorry extends AppCompatActivity {
    EditText edittext;
    TextView textView;
    Button btn;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_sorry);
            this.setTitle(R.string.activity_sorry);
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);

            editText= findViewById(R.id.editText);
            textView=findViewById(R.id.textView);
            btn=findViewById(R.id.btn);

            btn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                 String str = editText.getText().toString();
                 int i= Integer.parseInt(str);
                  String myText="";
                    for (int j=0; j<i;j++){
                        myText=myText.concat("Sorry \n");
                    }
                   textView.setText(myText);
                }
            });

        }

    };

Answer 2

The problem is in these lines:

String str = editText.getText().toString();
final int i= Integer.parseInt(str);

Your EditText is not yet created on the UI in the activity's onCreate method.

You need to read the value through some UI event, after the entire UI is formed.

For example, you can read the EditText when the button is clicked.

    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String str = editText.getText().toString();
            int i= Integer.parseInt(str);

            for (int j=0; j>i;j++){
                textView.setText("Sorry!");
            }
        }
    });

In the above code, the text inside the TextView will get overwritten after every loop. So for any value of i >= 1, you will only see a single "Sorry!" inside the TextView .