app crashes in real phone but works in emulator

Question

Hi i am new to android prgramming, so i wrote this simple code just to try it, it works just fine in android studio emulator but when i use build apk and install the app manually on my phone it crashes when i tap on the button i tried it in few phones with android 7, android 5 and andorid 4.4 all gave me the same result. I use android studio 3.0 and the minimum api i used android 4.0.3 for this project. what could be the problem.

package com.example.adem.myapplication;

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

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    void tst(View v) {
        TextView t= this.findViewById(R.id.temo);
        t.setText("he");
    }
}

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="com.example.adem.myapplication.MainActivity">

<TextView
    android:id="@+id/temo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent"/>

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="168dp"
    android:layout_marginTop="164dp"
    android:text="Button"
    android:onClick="tst"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"/>
</android.support.constraint.ConstraintLayout>

where i can find the log or the details because i am new to programming. — dark.semiQ, Nov 10 '17 at 10:02
Read this: https://developer.android.com/studio/debug/am-logcat.html — Blundell, Nov 10 '17 at 10:22
Filter your logcat by errors logs. Then you should find stacktrace easily. — Karol Kulbaka, Nov 10 '17 at 10:25
i used build apk and installed it manually on my phone not by avd manager — dark.semiQ, Nov 10 '17 at 10:28
Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Kriti, Nov 10 '17 at 10:31
the app crashes when i click on the button not when the app loads — dark.semiQ, Nov 10 '17 at 10:37
Set your phone on debug mode(on developer options). Then plug it to computer. Launch Android Studio and set error filter on your logcat. Launch app and press button. You will find your stacktrace and then send it. — Karol Kulbaka, Nov 10 '17 at 10:56

score 0 · Accepted Answer · answered Nov 10 '17 at 11:30

0

thank you guys for replying i found the problem that i was not setting function tst to public this the solution

public void tst(View view){
    TextView t= this.findViewById(R.id.temo);
    t.setText("he");
}

answered Nov 10 '17 at 11:30

dark.semiQ

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app crashes in real phone but works in emulator

1 Answers1