-1
チェックボックスがオンになっているかどうかを検出したいのですが、Checkboxでの操作でAndroidでエラーが発生しています
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://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.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)
setOncheckedListener（）、.onChecked（）などのチェックボックス操作がない場合、アプリケーションが正しく実行され、アクティビティにチェックボックスが表示されます。しかし、チェックボックス変数にメソッドを追加すると、アプリケーションが起動し、「残念なことに、TrackBlueは応答を停止しました」というメッセージですぐに停止します。また、私はエラーの原因を把握することができません。
可能な重複に変更して、[何NullPointerExceptionがある、と私はそれをどのように修正すればよいです？]（http://stackoverflow.com/questions/218384/what-is- - ヌルポイントのレセプションと方法 - 私はそれを修正する） – Denny