I want to detect whether if a checkbox is checked or not.
MainActivity.java
package com.example.vivek.trackblue;
import android.bluetooth.BluetoothAdapter;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import static android.bluetooth.BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE;
import static android.bluetooth.BluetoothAdapter.ACTION_REQUEST_ENABLE;
public class MainActivity extends AppCompatActivity{
final int Request_code = 1;
BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
private static int flag_bt_state = 0;
Button button2;
ImageView cold2;
@Override
protected void onCreate(Bundle savedInstanceState) {
// All local views declared here
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final Button button = (Button)findViewById(R.id.button5);
final Toast bt_disabled = Toast.makeText(getApplicationContext(), "Bluetooth Disabled", Toast.LENGTH_SHORT);
button2 = button;
final ImageView cold = (ImageView)findViewById(R.id.imageView);
cold2 = cold;
CheckBox cb1 = (CheckBox)findViewById(R.id.checkbox);
//Bluetooth Adapter State
if(bt.isEnabled()) {
flag_bt_state = 1;
button.setText("Stop Bluetooth");
cold.setImageResource(R.color.green);
}
else if(!bt.isEnabled()){
flag_bt_state=0;
button.setText("Start Bluetooth");
cold.setImageResource(R.color.red);
}
//Bluetooth Button Click Listener
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(bt.isEnabled()) {
flag_bt_state = 1;
button.setText("Stop Bluetooth");
cold.setImageResource(R.color.green);
}
else if(!bt.isEnabled()){
flag_bt_state=0;
button.setText("Start Bluetooth");
cold.setImageResource(R.color.red);
}
if(flag_bt_state==0 ){
Intent enableBtIntent = new
Intent(ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, Request_code);
button.setText("Stop Bluetooth");
flag_bt_state=1;
cold.setImageResource(R.color.green);
}
else if(flag_bt_state==1){
button.setText("Start Bluetooth");
bt.disable();
bt_disabled.show();
flag_bt_state=0;
cold.setImageResource(R.color.red);
}
}
});
cb1.setChecked(true);
// cb1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
// @Override
// public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
// if(b){
// Toast.makeText(getApplicationContext(), "checked", Toast.LENGTH_SHORT).show();
//
// }else{
// Toast.makeText(getApplicationContext(), "unchecked", Toast.LENGTH_SHORT).show();
// }
// }
//});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
Toast bt_enabled = Toast.makeText(getApplicationContext(), "Bluetooth Enabled", Toast.LENGTH_SHORT);
Toast bt_Permission_denied = Toast.makeText(getApplicationContext(), "Permission Denied", Toast.LENGTH_SHORT);
super.onActivityResult(requestCode, resultCode, data);
if(requestCode == Request_code){
if(resultCode == RESULT_OK){
bt_enabled.show();
cold2.setImageResource(R.color.green);
}
else
{
bt_Permission_denied.show();
flag_bt_state = 0;
button2.setText("Start Bluetooth");
cold2.setImageResource(R.color.red);
}
}
}
}
Layoutfile.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://ift.tt/nIICcg"
xmlns:app="http://ift.tt/GEGVYd"
xmlns:tools="http://ift.tt/LrGmb4"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.vivek.trackblue.MainActivity"
tools:layout_editor_absoluteY="81dp"
tools:layout_editor_absoluteX="0dp">
<ImageView
android:id="@+id/imageView"
android:layout_width="155dp"
android:layout_height="39dp"
android:src="@color/red"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.034" />
<Button
android:id="@+id/button5"
android:layout_width="152dp"
android:layout_height="40dp"
android:text="Start Bluetooth"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.034"
tools:layout_constraintRight_creator="1"
tools:layout_constraintLeft_creator="1" />
<CheckBox
android:id="@+id/checkBox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginLeft="16dp"
android:layout_marginRight="8dp"
android:layout_marginTop="8dp"
android:text="Make Device Discoverable"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintHorizontal_bias="0.471"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.125" />
</android.support.constraint.ConstraintLayout>
logcat
05-01 18:42:17.017 12720-12720/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.vivek.trackblue, PID: 12720
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.vivek.trackblue/com.example.vivek.trackblue.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.CheckBox.setChecked(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3163)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3273)
at android.app.ActivityThread.access$1000(ActivityThread.java:219)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1735)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6959)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.CheckBox.setChecked(boolean)' on a null object reference
at com.example.vivek.trackblue.MainActivity.onCreate(MainActivity.java:100)
at android.app.Activity.performCreate(Activity.java:6609)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3116)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3273)
at android.app.ActivityThread.access$1000(ActivityThread.java:219)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1735)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6959)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
when there is no checkbox operations like setOncheckedListener(), .onChecked(), etc, the application runs correctly and displays the checkbox in the Activity. But when I add a method to the checkbox variable the app starts and immediately stops with the message "Unfortunately, TrackBlue stopped responding". Also I am unable to figure out the source of the error.
Aucun commentaire:
Enregistrer un commentaire