App crashing when i try to change activity Intent
Question
I've been trying to fix this for weeks but failed, when I click on login (indicated with the id "lin") to open a new activity the app crash, i don't know if it's a problem with the Intent or something else, here is the code. The manifest should be ok so I think it's a problem in the MainActivity with Intent ab. The other activity is called Qrcode. I tried to change appcompatactivty to activity but didn't work, i don't really know what to do.
Edit: I posted the code of the qrcode activity, i got it from the answers of this question: Android, How to read QR code in my application? , only for educational purpose of course.
Edit 2: logcat posted, sorry for any issues with asking this question, it's the first question i ask here.
Logcat
2021-06-04 10:08:06.177 27399-27399/? I/h24distributor: Late-enabling -Xcheck:jni
2021-06-04 10:08:06.197 27399-27399/? I/h24distributor: Unquickening 21 vdex files!
2021-06-04 10:08:06.204 27399-27399/? E/h24distributor: Unknown bits set in runtime_flags: 0x800000
2021-06-04 10:08:06.343 27399-27399/? I/Perf: Connecting to perf service.
2021-06-04 10:08:06.360 27399-27399/? D/NetworkSecurityConfig: No Network Security Config specified, using platform default
2021-06-04 10:08:06.360 27399-27399/com.example.h24distributori D/NetworkSecurityConfig: No Network Security Config specified, using platform default
2021-06-04 10:08:06.386 27399-27399/com.example.h24distributori E/Config:Grabber:OnePlusFontConfig: Index 0 requested, with a size of 0
2021-06-04 10:08:06.417 27399-27399/com.example.h24distributori E/h24distributor: [frame_perf] perfboost open tb_ctl file failed, isApp[1], errno=No such file or directory
2021-06-04 10:08:06.418 27399-27399/com.example.h24distributori E/libprocessgroup: set_timerslack_ns write failed: Operation not permitted
2021-06-04 10:08:06.465 27399-27399/com.example.h24distributori E/h24distributor: Invalid ID 0x00000000.
2021-06-04 10:08:06.465 27399-27399/com.example.h24distributori E/h24distributor: Invalid ID 0x00000000.
2021-06-04 10:08:06.495 27399-27399/com.example.h24distributori E/h24distributor: Invalid ID 0x00000000.
2021-06-04 10:08:06.497 27399-27399/com.example.h24distributori I/chatty: uid=10692(com.example.h24distributori) identical 1 line
2021-06-04 10:08:06.497 27399-27399/com.example.h24distributori E/h24distributor: Invalid ID 0x00000000.
2021-06-04 10:08:06.506 27399-27399/com.example.h24distributori E/h24distributor: Invalid ID 0x00000000.
2021-06-04 10:08:06.506 27399-27399/com.example.h24distributori I/chatty: uid=10692(com.example.h24distributori) identical 1 line
2021-06-04 10:08:06.507 27399-27399/com.example.h24distributori E/h24distributor: Invalid ID 0x00000000.
2021-06-04 10:08:06.541 27399-27399/com.example.h24distributori I/OPFD_Manager: Dark? false, OP Force ? false
2021-06-04 10:08:06.542 27399-27399/com.example.h24distributori V/ViewRootImpl: The specified message queue synchronization barrier token has not been posted or has already been removed
2021-06-04 10:08:06.608 27399-27399/com.example.h24distributori D/ViewRootImpl: support adaptive color gamut feature!
2021-06-04 10:08:06.646 27399-9660/com.example.h24distributori I/AdrenoGLES-0: QUALCOMM build : 559e78c, Ib9d997268a
Build Date : 10/13/20
OpenGL ES Shader Compiler Version: EV031.32.02.02
Local Branch : mybrancheb0d76cb-f27a-f1ff-9cdc-1458d0b52ae8
Remote Branch : quic/gfx-adreno.lnx.1.0.r99-rel
Remote Branch : NONE
Reconstruct Branch : NOTHING
2021-06-04 10:08:06.646 27399-9660/com.example.h24distributori I/AdrenoGLES-0: Build Config : S P 10.0.7 AArch64
2021-06-04 10:08:06.646 27399-9660/com.example.h24distributori I/AdrenoGLES-0: Driver Path : /vendor/lib64/egl/libGLESv2_adreno.so
2021-06-04 10:08:06.654 27399-9660/com.example.h24distributori I/AdrenoGLES-0: PFP: 0x016ee190, ME: 0x00000000
2021-06-04 10:08:06.740 27399-27399/com.example.h24distributori D/DecorView: onWindowFocusChangedFromViewRoot hasFocus: true, DecorView@a86767f[MainActivity]
2021-06-04 10:08:06.743 27399-27399/com.example.h24distributori D/ViewRootImpl[MainActivity]: windowFocusChanged hasFocus=true inTouchMode=true
2021-06-04 10:08:15.552 27399-9660/com.example.h24distributori W/DisplayEventDispatcher: dispatcher 0xb4000077f19b29f0 ~ ignoring unknown event type 0x6d746f6e
2021-06-04 10:08:15.552 27399-27399/com.example.h24distributori W/DisplayEventDispatcher: dispatcher 0xb4000077a19c5930 ~ ignoring unknown event type 0x6d746f6e
2021-06-04 10:08:15.927 27399-27399/com.example.h24distributori D/ViewRootImpl[MainActivity]: windowFocusChanged hasFocus=false inTouchMode=true
2021-06-04 10:08:41.340 27399-27399/com.example.h24distributori D/ActivityThread: pid:27399 tid:27399 doframe Callback
2021-06-04 10:08:41.351 27399-9660/com.example.h24distributori W/DisplayEventDispatcher: dispatcher 0xb4000077f19b29f0 ~ ignoring unknown event type 0x6d746f6e
2021-06-04 10:08:41.351 27399-27399/com.example.h24distributori W/DisplayEventDispatcher: dispatcher 0xb4000077a19c5930 ~ ignoring unknown event type 0x6d746f6e
2021-06-04 10:08:41.530 27399-27399/com.example.h24distributori D/DecorView: onWindowFocusChangedFromViewRoot hasFocus: true, DecorView@a86767f[MainActivity]
2021-06-04 10:08:41.531 27399-27399/com.example.h24distributori D/ViewRootImpl[MainActivity]: windowFocusChanged hasFocus=true inTouchMode=true
2021-06-04 10:08:42.117 27399-27399/com.example.h24distributori D/AndroidRuntime: Shutting down VM
2021-06-04 10:08:42.118 27399-27399/com.example.h24distributori E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.h24distributori, PID: 27399
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.h24distributori/com.example.h24distributori.Qrcode}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3611)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3775)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2246)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:233)
at android.app.ActivityThread.main(ActivityThread.java:8010)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:631)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:978)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.h24distributori.Qrcode.onCreate(Qrcode.java:59)
at android.app.Activity.performCreate(Activity.java:8006)
at android.app.Activity.performCreate(Activity.java:7990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1329)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3584)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3775)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2246)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:233)
at android.app.ActivityThread.main(ActivityThread.java:8010)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:631)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:978)
2021-06-04 10:08:42.149 27399-27399/com.example.h24distributori I/Process: Sending signal. PID: 27399 SIG: 9
MainActivity
import androidx.appcompat.app.AppCompatActivity;
import android.app.Activity;
import android.os.Bundle;
import android.widget.EditText;
import android.widget.TextView;
import android.content.Intent;
import android.graphics.Typeface;
//import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends Activity {
EditText pswd,usrusr;
TextView sup,lin;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lin = (TextView) findViewById(R.id.lin);
usrusr = (EditText) findViewById(R.id.usrusr);
pswd = (EditText) findViewById(R.id.pswrdd);
sup = (TextView) findViewById(R.id.sup);
lin.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick (View v)
{
Intent ab = new Intent(MainActivity.this, Qrcode.class);
startActivity(ab);
}
});
sup.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick (View v)
{
Intent it = new Intent(MainActivity.this, Signup.class);
startActivity(it);
}
});
}
}
Activity main layout
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
android:background="@drawable/grdnt"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:paddingLeft="60dp"
android:paddingRight="60dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:padding="16dp">
<ImageView
android:layout_width="20dp"
android:layout_height="20dp"
android:src="@drawable/usrusr"
android:layout_gravity="center"/>
<EditText
android:id="@+id/usrusr"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Username"
android:textColorHint="#d9e5f3"
android:layout_marginLeft="15dp"
android:background="#00000000"
android:letterSpacing="0.1"
android:textSize="16dp"
android:inputType="text"
android:textColor="#fff"
/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="#4a5a71"></LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:padding="16dp">
<ImageView
android:layout_width="20dp"
android:layout_height="20dp"
android:src="@drawable/pswd"
android:layout_gravity="center"/>
<EditText
android:id="@+id/pswrdd"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Password"
android:textColorHint="#d9e5f3"
android:layout_marginLeft="15dp"
android:background="#00000000"
android:inputType="textPassword"
android:letterSpacing="0.1"
android:textSize="16dp"
android:textColor="#fff"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="#4a5a71"></LinearLayout>
</LinearLayout>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="60dp"
android:paddingRight="60dp"
android:orientation="vertical"
android:gravity="bottom"
android:layout_marginBottom="20dp">
<TextView
android:id="@+id/lin"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#009a9a"
android:text="Login"
android:textColor="#d9e5f3"
android:textStyle="bold"
android:gravity="center"
android:layout_gravity="bottom"
android:padding="16dp"
android:layout_marginBottom="50dp"
android:letterSpacing="0.2"/>
<TextView
android:id="@+id/sup"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="Non hai un account? Registrati"
android:textColor="#d9e5f3"
android:letterSpacing="0.1"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:layout_marginBottom="400dp">
<ImageView
android:layout_width="150dp"
android:layout_height="150dp"
android:src="@drawable/logo_large"
/>
</LinearLayout>
</RelativeLayout>
Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.h24distributori">
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme"
android:usesCleartextTraffic="true">
<activity android:name=".Qrcode"></activity>
<activity android:name=".Signup" />
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Qrcode activity:
package com.example.h24distributori;
import androidx.appcompat.app.AppCompatActivity;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.MultiFormatWriter;
import com.google.zxing.WriterException;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.integration.android.IntentIntegrator;
import com.google.zxing.integration.android.IntentResult;
public class Qrcode extends Activity {
ImageView imageView;
Button button;
Button btnScan;
EditText editText;
String EditTextValue ;
Thread thread ;
public final static int QRcodeWidth = 350 ;
Bitmap bitmap ;
TextView tv_qr_readTxt;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_qrcode);
imageView = (ImageView)findViewById(R.id.imageView);
editText = (EditText)findViewById(R.id.editText);
button = (Button)findViewById(R.id.button);
btnScan = (Button)findViewById(R.id.btnScan);
tv_qr_readTxt = (TextView) findViewById(R.id.tv_qr_readTxt);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(!editText.getText().toString().isEmpty()){
EditTextValue = editText.getText().toString();
try {
bitmap = TextToImageEncode(EditTextValue);
imageView.setImageBitmap(bitmap);
} catch (WriterException e) {
e.printStackTrace();
}
}
else{
editText.requestFocus();
Toast.makeText(Qrcode.this, "Please Enter Your Scanned Test" , Toast.LENGTH_LONG).show();
}
}
});
btnScan.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
IntentIntegrator integrator = new IntentIntegrator(Qrcode.this);
integrator.setDesiredBarcodeFormats(IntentIntegrator.ALL_CODE_TYPES);
integrator.setPrompt("Scan");
integrator.setCameraId(0);
integrator.setBeepEnabled(false);
integrator.setBarcodeImageEnabled(false);
integrator.initiateScan();
}
});
}
Bitmap TextToImageEncode(String Value) throws WriterException {
BitMatrix bitMatrix;
try {
bitMatrix = new MultiFormatWriter().encode(
Value,
BarcodeFormat.DATA_MATRIX.QR_CODE,
QRcodeWidth, QRcodeWidth, null
);
} catch (IllegalArgumentException Illegalargumentexception) {
return null;
}
int bitMatrixWidth = bitMatrix.getWidth();
int bitMatrixHeight = bitMatrix.getHeight();
int[] pixels = new int[bitMatrixWidth * bitMatrixHeight];
for (int y = 0; y < bitMatrixHeight; y++) {
int offset = y * bitMatrixWidth;
for (int x = 0; x < bitMatrixWidth; x++) {
pixels[offset + x] = bitMatrix.get(x, y) ?
getResources().getColor(R.color.QRCodeBlackColor):getResources().getColor(R.color.QRCodeWhiteColor);
}
}
Bitmap bitmap = Bitmap.createBitmap(bitMatrixWidth, bitMatrixHeight, Bitmap.Config.ARGB_4444);
bitmap.setPixels(pixels, 0, 350, 0, 0, bitMatrixWidth, bitMatrixHeight);
return bitmap;
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
IntentResult result = IntentIntegrator.parseActivityResult(requestCode, resultCode, data);
if(result != null) {
if(result.getContents() == null) {
Log.e("Scan*******", "Cancelled scan");
} else {
Log.e("Scan", "Scanned");
tv_qr_readTxt.setText(result.getContents());
Toast.makeText(this, "Scanned: " + result.getContents(), Toast.LENGTH_LONG).show();
}
} else {
// This is important, otherwise the result will not be passed to the fragment
super.onActivityResult(requestCode, resultCode, data);
}
}
}
2 answers
solution1
0 2021-06-03 17:42:29
ur code in MainActivity seems ok and I think don't have any problem. In my opinion your Qrcode Activity has some bugs in it, like onCreate method, you should see the Logcat logs in android Studio, btw u can attach the Qrcode activity codes here, it is really helpful. another way to find the bug is by using the try-catch in your code and log the exception
solution2
0 ACCPTED 2021-06-07 07:18:32
Here's the error
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at com.example.h24distributori.Qrcode.onCreate(Qrcode.java:59)
What does it mean? You are trying to setOnClickListener on a null object reference.
Check the next line in the log
at com.example.h24distributori.Qrcode.onCreate(Qrcode.java:59)
"QrCode.java:59" This means that the error is in QrCode activity on line 59.
You are setting a onclicklistener to 'button' on line 59. This means that 'button' variable is null.
But I can see that you have initialized the button variable
button = (Button)findViewById(R.id.button);
So why is it still null? There is no button with id R.id.button, so findViewById() returns null. Check the QrCode activity layout xml
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