I have the problem, that whenever I try to add any Listener onto my ToggleButton, the App is not even starting and just crashing. In this Codeexample I tried it with an setOnCheckedChangeListener.
It is already crashing, when I just set this even without any Listener:
tglButton = (ToggleButton)findViewById(R.id.tglBtn);
MainActivity.java
package com.example.paulii.myapplication2;
import android.content.Intent;
import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
import android.widget.ToggleButton;
public class MainActivity extends AppCompatActivity {
ListView mListView;
Button button_stpd;
DBAdapter myDB;
Button btn_delete;
ToggleButton tglButton;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
openDB();
populateListView();
button_stpd = (Button)findViewById(R.id.btn_createNewAlarm);
button_stpd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, createNewWecker.class);
startActivity(intent);
}
});
mListView = (ListView)findViewById(R.id.stationList);
mListView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
myDB.deleteRow(id);
populateListView();
return false;
}
});
btn_delete = (Button)findViewById(R.id.btn_delete);
btn_delete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
myDB.deleteAll();
populateListView();
}
});
tglButton = (ToggleButton)findViewById(R.id.tglBtn);
tglButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
Toast.makeText(getApplicationContext(), String.valueOf(buttonView.isChecked()),Toast.LENGTH_SHORT).show();
}
});
}
public void populateListView(){
Cursor cursor = myDB.getAllRows();
String[] fromFieldNames = new String[]{DBAdapter.KEY_TASK};
int[] toViewIDs = new int[]{R.id.textStation};
SimpleCursorAdapter myCursorAdapter;
myCursorAdapter = new SimpleCursorAdapter(getBaseContext(), R.layout.textview_list, cursor, fromFieldNames, toViewIDs,0);
ListView myList = (ListView)findViewById(R.id.stationList);
myList.setAdapter(myCursorAdapter);
}
@Override
protected void onStop() {
super.onStop();
}
private void openDB(){
myDB = new DBAdapter(this);
myDB.open();
}
private void closeDB(){
myDB.close();
}
@Override
public void onDestroy() {
super.onDestroy();
closeDB();
}
}
As you can see, I try to add the setOnCheckedChangeListener to the tglButton as always. But I don´t understand why the Application is crashing after that.
I created the button in the textview_list.xml layout. Is the problem, that I can´t access that button from my MainActivity?
activity_main
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_testwindow"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.paulii.myapplication2.MainActivity">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:weightSum="1"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="282dp"
android:layout_weight="1.07"
android:weightSum="1">
<RelativeLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="0.72"
android:weightSum="1"
tools:ignore="NestedWeights,UselessParent"
android:layout_marginBottom="10dp">
<ListView
android:layout_width="match_parent"
android:id="@+id/stationList"
android:layout_gravity="left"
tools:ignore="RtlHardcoded"
android:layout_height="400dp" />
<Button
android:text="Delete All"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/btn_delete"
android:layout_alignBottom="@+id/btn_createNewAlarm"
android:layout_alignParentEnd="true" />
<Button
android:text="@string/create_new_alarm"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/btn_createTimePicker"
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true" />
</RelativeLayout>
</LinearLayout>
</LinearLayout>
</RelativeLayout>
textview_list.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="horizontal" android:layout_width="match_parent"
android:layout_height="match_parent"
android:weightSum="1">
<TextView
android:text="TextView"
android:layout_width="150dp"
android:id="@+id/textStation"
android:layout_height="68dp"
android:layout_weight="0.87" />
<ToggleButton
android:text="ToggleButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/tglBtn"
android:focusable="false" />
</LinearLayout>
The ErrorMessage is:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.paulii.myapplication2/com.example.paulii.myapplication2.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
Maybe some of you can help me out?
