I am a beginner of Android, but I am studying the voting app, but I don't know what to do...
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.abc, PID: 15185
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.abc/com.example.abc.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.abc.MainActivity.onCreate(MainActivity.java:30)
at android.app.Activity.performCreate(Activity.java:8000)
at android.app.Activity.performCreate(Activity.java:7984)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
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$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Error content.
package com.example.abc;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
Button btn;
int vCount[] =new int[6];
ImageView[] imgV = new ImageView[6];
int[] imgID = {R.id.img1, R.id.img2, R.id.img3, R.id.img4, R.id.img5, R.id.img6};
String Name[] = {"Chris", "Brown", "Arab", "Chulsu", "Eunsu", "Kangmin"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
android:setTitle ("Leader Election Vote");
btn = (Button)findViewById(R.id.btn);
for (int i=0; i<imgID.length; i++) {
final int index;
index = i;
imgV[index] = (ImageView) findViewById(imgID[index]);
**imgV[index].setOnClickListener(new View.OnClickListener() {**
@Override
public void onClick(View view) {
vCount[index]++;
Toast.makeText(getApplicationContext(),Name[index] + "I voted for you.",
Toast.LENGTH_SHORT).show();
}
});
}
btn = (Button) findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(getApplicationContext(), resultvote.class);
intent.putExtra("vCount", vCount);
intent.putExtra("Name", Name);
startActivity(intent);
}
});
}
The error message is Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on null
imgV[index].setOnClickListener(
), so imgV[index]
is null somewhere. It comes from findViewById
, so maybe there is something wrong with the resource name.
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