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Pressing a button does not change the value of textview

This is the XML code:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".MainActivity" > <TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:gravity="center" android:text="Your total is 0" android:textSize="20dp" /> <Button android:id="@+id/button2" android:layout_width="250dp" android:layout_height="wrap_content" android:layout_alignLeft="@+id/button1" android:layout_centerVertical="true" android:text="Subtract one" android:textSize="20dp" /> <Button android:id="@+id/button1" android:layout_width="250dp" android:layout_height="wrap_content" android:layout_below="@+id/textView1" android:layout_centerHorizontal="true" android:layout_marginTop="62dp" android:text="Add one" android:textSize="20dp" />

This is the java code:

 package com.example.helloworld; import android.os.Bundle; import android.app.Activity; import android.view.Menu; import android.view.View; import android.widget.Button; import android.widget.TextView; public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } int counter; Button add, sub; TextView display; @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); counter = 0; add = (Button) findViewById(R.id.button1); sub = (Button) findViewById(R.id.button2); display = (TextView) findViewById(R.id.textView1); add.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter++; display.setText("Your total is " + counter); } }); sub.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter--; display.setText("Your total is " + counter); } }); return true; } }

When I click the buttons, nothing happens with the text of the text.

Please, help. I want the display to show the counter value after adding or subtracting, depending on which button was pressed.

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5 answers

You put your code in the wrong place. You do not work with the menu, so you do not need to place it in the public boolean onCreateOptionsMenu(Menu menu) {} , the button will not receive any action / fire

move this

 counter = 0; add = (Button) findViewById(R.id.button1); sub = (Button) findViewById(R.id.button2); display = (TextView) findViewById(R.id.textView1); add.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter++; display.setText("Your total is " + counter); } }); sub.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter--; display.setText("Your total is " + counter); } });

to your onCreate () method and try running it again

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Problem:

The android documentation says it is supposed to use findViewById in onCreate:

onCreate (Bundle) is where you initialize your activity. Most importantly, here you usually call setContentView (int) with a layout resource that defines your user interface, and using findViewById (int) to get widgets in that user interface that you need to interact programmatically with.

But you use them in CreateOptionsMenu. Complete the following steps:

First do these ad class levels:

 public class MainActivity extends Activity { int counter; Button add, sub; TextView display; //......more code below

Move this piece of code to onCreate(Bundle savedInstanceState) { instead of onCreateOptionsMenu(Menu menu) { . especially counter code

  @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //assigning initial value to counter counter = 0;//counter set //getting the controls add = (Button) findViewById(R.id.button1); sub = (Button) findViewById(R.id.button2); display = (TextView) findViewById(R.id.textView1); //setting Listeners add.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter++; display.setText("Your total is " + counter); } }); sub.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter--; display.setText("Your total is " + counter); } }); }
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 public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); counter = 0; add = (Button) findViewById(R.id.button1); sub = (Button) findViewById(R.id.button2); display = (TextView) findViewById(R.id.textView1); add.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter++; display.setText("Your total is " + counter); } }); sub.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter--; display.setText("Your total is " + counter); } }); } int counter; Button add, sub; TextView display; @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; } }
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All things in the onCreate method are not in onCreateOptionsMenu, as follows

// below code

 int counter; Button add, sub; TextView display; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); counter = 0; add = (Button) findViewById(R.id.button1); sub = (Button) findViewById(R.id.button2); display = (TextView) findViewById(R.id.textView1); add.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter++; display.setText("Your total is " + counter); } }); sub.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter--; display.setText("Your total is " + counter); } }); } @Override public boolean onCreateOptionsMenu(Menu menu) { return true; } }
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You need to complete your task in the onCreate method. The onCreateOptionsMenu (menu) method is used to task the task in the options menu. So replace your code inside the onCreate method. The full code is given below. Replace it and try. Hope it works :)

  package com.example.helloworld; import android.os.Bundle; import android.app.Activity; import android.view.Menu; import android.view.View; import android.widget.Button; import android.widget.TextView; public class MainActivity extends Activity { int counter; Button add, sub; TextView display; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); counter = 0; add = (Button) findViewById(R.id.button1); sub = (Button) findViewById(R.id.button2); display = (TextView) findViewById(R.id.textView1); add.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter++; display.setText("Your total is " + counter); } }); sub.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub counter--; display.setText("Your total is " + counter); } }); } @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; } }

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Source: https://habr.com/ru/post/1468900/

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