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App crashes when trying to call SetSupportActionBar

I have made an app that works fine and uses a default toolbar. However I want to add navigation buttons to this toolbar so I am implementing my own that I can inflate a menu onto it. However when I try to call SetSupportActionBar() the app crashes.
I have tried to set the app to not use the default action bar in both the manifest: <activity android:name=".MainMenu" android:theme="#style/Theme.AppCompat.NoActionBar"/> as well as in the XML file: android:theme="#style/Theme.AppCompat.NoActionBar", as this was the suggested solution for someone else with a similar issue however this has not worked.
The code I am using is as follows;
XML:
<Toolbar
android:id="#+id/my_toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
Java:
public class MainMenu extends AppCompatActivity {
Toolbar mToolbar;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_menu);
mToolbar = findViewById(R.id.my_toolbar);
setSupportActionBar(mToolbar);
mToolbar.setNavigationIcon(R.drawable.menu_arrow);
mToolbar.setNavigationOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
}
});
}
}

Change the toolbar's xml to:
<android.support.v7.widget.Toolbar
android:id="#+id/my_toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
instead of Toolbar
also look at your imports, if you have this line:
import android.widget.Toolbar;
replace it with:
import android.support.v7.widget.Toolbar;

How do i get a button to open a new activity in android studio?

I'd seen this asked in many, many places and have tried to follow the instructions given to no avail. I dont know if the questions are old, i'm doing things incorrectly or if my android studio program isnt working. What i want to do is to only open a new activity when a button is clicked. I'm very new to developing android applications.
I've recently tried to follow the answer provided here: How do I get a button to open another activity in Android Studio?
OnClick on the button is called "goTutorials"
My original activity is called home (Not mainActivity)
The new one is called tutorials.
This is what i added from trying to follow the link above:
In home's java file:
btn = (Button)findViewById(R.id.open_activity_button);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(home.this, tutorials.class));
}
});
In manifest file:
<activity
android:name="tutorials"
android:label="#string/app_name">
</activity>

Method 1
Use the onclick attribute in XML (so that whenever you click the button, defined method will trigger)
Step 1. - go to the XML where you button is(activity_home) & add
<Button
............
android:onClick="gotoTutorial"/>
Step 2. - then go to the home.Java & add following
public void gotoTutorial(View v){
Intent tutorialPage = new Intent (this, tutorials.class);
startActivity(tutorialPage);
}
Method 2
Use the setOnClickListener
Step 1. -
//create the link to the button in the interface
btn_tutorial = (Button)findViewById(R.id.tutorial_button);
btn_tutorial.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent tutorialPage = new Intent (this, tutorials.class);
startActivity(tutorialPage);
}
}

I have created a sample app please see the code below.
You need to specify information of all activities in Manifest file.
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.nextech.startnewactivity">
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".TutorialsActivity"
android:label="#string/title_activity_tutorials"
android:theme="#style/AppTheme.NoActionBar"></activity>
</application>
</manifest>
My Launcher activity is MainActivity.java
package com.nextech.startnewactivity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button startTutorials = (Button)findViewById(R.id.startTutorials);
startTutorials.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent tutorialsActivityIntent = new Intent(MainActivity.this,TutorialsActivity.class);
MainActivity.this.startActivity(tutorialsActivityIntent);
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
activity_main.xml
<?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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="com.nextech.startnewactivity.MainActivity"
tools:showIn="#layout/activity_main">
<TextView android:id="#+id/welcomeText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="20dp"
android:layout_centerHorizontal="true"
android:text="Hello World! This is main activity!" />
<Button android:id="#+id/startTutorials"
android:layout_below="#+id/welcomeText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:text="Start Tutorials"/>
</RelativeLayout>
TutorialsActivity.java
package com.nextech.startnewactivity;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
public class TutorialsActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tutorials);
}
}
activity_tutorials.xml
<?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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="com.nextech.startnewactivity.TutorialsActivity"
tools:showIn="#layout/activity_tutorials">
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="This is tutorial activity"
android:layout_centerInParent="true"/>
</RelativeLayout>
I hope it helps.

Your manifest file is not displaying, but make sure you add the activity in your manifest AndroidManifest.xml in the application field. Here's an example from Google: Link
<application ... >
...
<activity
android:name="com.mycompany.myfirstapp.DisplayMessageActivity"
android:label="#string/title_activity_display_message"
android:parentActivityName="com.mycompany.myfirstapp.MyActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.mycompany.myfirstapp.MyActivity" />
</activity>
Otherwise, the method you're using should be correct. You create an intent to the class of the Activity you want to start.
Intent intent = new Intent(this, tutorials.class);
startActivity(intent);
Make sure you have the necessary methods such as onCreate(Bundle savedInstance) Overrided.
Note that in the sample above android:name="" is your activity's full path name to the class (without .class/.java) and label is going to be the action toolbar string you'll see. In the <meta-data/> section you can alter the android:value="" to the starting activity's name so that will need to change based on what you call it.
Finally, make sure it has an XML view to go with it, as it gets inflated in the onCreate(Bundle savedInstance) call.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_layout_here);
}

inside your activity file write this
Button btn = (Button)findViewById(R.id.open_activity_button);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(home.this, tutorials.class));
}
});

XML
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send"
android:onClick="sendMessage" />
.Java class
/** Called when the user clicks the Send button */
public void sendMessage(View view) {
Intent intent = new Intent(this, YourActivityYouWantToOpen.class);
startActivity(intent);
}

Unknown Crashing

I am currently trying to develop a simple feature for switching from one page to another but every time I launch the app it crashes.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Screen One......"
android:textAppearance="?android:attr/textAppearanceLarge" />
<Button
android:id="#+id/scan"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Click me to another screen" />
</LinearLayout>
MainActivity.java
package com.example.mdpmk1;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Button;
import android.view.View;
import android.view.View.OnClickListener;
public class MainActivity extends Activity {
Button button;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addListenerOnButton();
}
public void addListenerOnButton() {
final Context context = this;
button = (Button) findViewById(R.id.scan);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent = new Intent(context, ScanScreen.class);
startActivity(intent);
}
});
}
}
ScanScreen.java
package com.example.mdpmk1;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
public class ScanScreen extends Activity {
Button button;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.scan_screen);
}
}
scan_screen.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="You have done it!!"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
Im quite new to this sort of stuff but i am doing an app for my major at school and would like to have it actually working. Any help would be lovely. Thanks

You forgot to write following statement in your MainActivity's onCreate() method,
setContentView(R.layout.activity_main);
Write here,
public class MainActivity extends Activity
{
Button button;
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); // You forgot this line
addListenerOnButton();
}
Also change following line of code,
public void onClick(View arg0)
{
Intent intent = new Intent( MainActivity.this, ScanScreen.class ); // Change here
startActivity(intent);
}

Try editing intent statement in class MainActivity to:
Intent intent = new Intent(MainActivity.this, ScanScreen.class);
startActivity(intent);
You must also add:
setContentView(R.layout.activity_main);
in your ActivityMain class onCreate function to set a view.

setContentView(R.your_layout) doesnt exists in your MainActivity's onCreate(). Try providing your activity a layout.

In your MainActivity onCreate you need to add
setContentView(R.layout.activity_main);

First of all, add SetContentView(R.layout.activity_main) in your MainActivity.OnCreate method befor call to addListenerOnButton.
then be sure that you add your activities entries in your manifest.xml and make MainActivity as your Main Application Activity, like below:
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<activity android:name=".ScanScreen"/>

Android - Admob test ads not appearing in app

I want to integrate Google Mobile Ads into my app, but when I debug it, whenever using my own device, or using an emulator, no ads appear.
I am using the code from Google's developer page: https://developers.google.com/mobile-ads-sdk/docs/admob/fundamentals
When looking at logcat, I find that my app is not requesting any ads, and Admob is reporting no requests.
What am I missing?
Here is my code
AndroidManifest
<application android:icon="#drawable/ic_launcher">
<meta-data android:name="com.google.android.gms.version"
android:value="#integer/google_play_services_version"/>
android:label="#string/app_name" >
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:screenOrientation="portrait"
android:configChanges="keyboard|keyboardHidden|orientation|screenSize">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name="com.google.android.gms.ads.AdActivity"
android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"/>
</application>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
</manifest>
layout - main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/adBanner"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads">
<com.google.ads.AdView android:id="#+id/ad"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
ads:adUnitId="-omitted-"
ads:adSize="BANNER" />
</LinearLayout>
AdBanner.java (the class with Google's example test code)
package com.google.android.gms.ads.banner;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdSize;
import com.google.android.gms.ads.AdView;
import -omitted-
import android.os.Bundle;
import android.widget.LinearLayout;
import -omitted-
public class AdBanner extends MainActivity{
/**
* A simple {#link Activity} that embeds an AdView.
*/
/** The view to show the ad. */
private AdView adView;
/* Your ad unit id. Replace with your actual ad unit id. */
private static final String AD_UNIT_ID = "-omitted-";
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Create an ad.
adView = new AdView(this);
adView.setAdSize(AdSize.BANNER);
adView.setAdUnitId(AD_UNIT_ID);
// Add the AdView to the view hierarchy. The view will have no size
// until the ad is loaded.
LinearLayout layout = (LinearLayout) findViewById(R.id.adBanner);
layout.addView(adView);
// Create an ad request. Check logcat output for the hashed device ID to
// get test ads on a physical device.
AdRequest adRequest = new AdRequest.Builder()
.addTestDevice(AdRequest.DEVICE_ID_EMULATOR)
.addTestDevice("-omitted-")
.build();
// Start loading the ad in the background.
adView.loadAd(adRequest);
}
#Override
public void onResume() {
super.onResume();
if (adView != null) {
adView.resume();
}
}
#Override
public void onPause() {
if (adView != null) {
adView.pause();
}
super.onPause();
}
/** Called before the activity is destroyed. */
#Override
public void onDestroy() {
// Destroy the AdView.
if (adView != null) {
adView.destroy();
}
super.onDestroy();
}
}

I have seen something strange in your code:
In your AdBanner.java you use this:
import com.google.android.gms.ads.AdView;
but in your layout you use:
<com.google.ads.AdView
which corresponds to old Admob, but seems you may want to use com.google.android.gms.ads.AdView in your layout instead

I think you must check the android logs to see if any errors or warnings are given for your admob. For example: I was not able to see the ads too and when i check the logs i found the "not enough space" warning for my advertisement. I was using the size "SMART_BANNER" that uses the width as 360dp (you can check the sizes here). So i changed my AdView's width to exact 360dp to solve my problem and it is now working: Stil
I hope this information helps. Just check the logs and also console.
In addition, my adView:
<com.google.android.gms.ads.AdView
xmlns:ads="http://schemas.android.com/apk/res-auto"
android:id="#+id/adView"
android:layout_width="360dp"
android:layout_height="wrap_content"
ads:adSize="SMART_BANNER"
ads:adUnitId="#string/banner_ad_unit_id" />
Best regards.

Android App won't display in Android Studio Emulator

I am very new to Android development. I have tried to recreate an app where if you press a button, a message "new text string" is displayed. However, when I run the AVD and choose the Virtual Device, it doesn't display it. Just an old TestApp I had. Can anyone suggest a fix? I'd really appreciate it.
My code:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android= "http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView android:id="#+id/hello_text"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/hello"
/>
<Button android:id="#+id/trigger"
android:layout_width="100dip" android:layout_height="100dip"
android:text="#string/button1"
android:layout_below="#+id/hello_text"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="111dp" />
</RelativeLayout>
SimpleActivity.java
package com.example.simpleactivityexample;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;
import android.widget.*;
import android.view.View;
public class SimpleActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Toast.makeText(this, "onCreate", Toast.LENGTH_SHORT).show();
Button startButton = (Button) findViewById(R.id.trigger);
startButton.setOnClickListener(new View.OnClickListener()
{
private TextView tv = (TextView) findViewById(R.id.hello_text);
public void onClick(View view)
{
tv.setText("new text string");
}
}
);
}
#Override
protected void onStart() {
super.onStart();
Toast.makeText(this, "onStart", Toast.LENGTH_SHORT).show();
}
#Override
protected void onResume() {
super.onResume();
Toast.makeText(this, "onResume", Toast.LENGTH_SHORT).show();
}
#Override
protected void onRestart() {
super.onRestart();
Toast.makeText(this, "onRestart", Toast.LENGTH_SHORT).show();
}
#Override
protected void onPause() {
Toast.makeText(this, "onPause", Toast.LENGTH_SHORT).show();
super.onPause();
}
#Override
protected void onStop() {
Toast.makeText(this, "onStop", Toast.LENGTH_SHORT).show();
super.onStop();
}
#Override
protected void onDestroy() {
Toast.makeText(this, "onDestroy", Toast.LENGTH_SHORT).show();
super.onDestroy();
}
}
Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.simpleactivityexample" >
<application
android:debuggable="true"
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.simpleactivityexample.SimpleActivity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:label="#string/app_name"
android:theme="#style/FullscreenTheme" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Strings.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">Dietary Application</string>
<string name="hello">Hello!</string>
<string name="button1">This is a button!</string>
</resources>

I managed to solve it.I am using Android Studio by the way.
I went to the run tab at the top of the screen and went into ''Edit Configurations''. I then ticked ''Show chooser dialog''. I started the AVD and when it was fully started, A pressed the run function(green triangle) and it started on the Android. Thanks so much to everyone who helped!

Your code seems fine; check the logcat and console outputs when you click 'Run as Android Application' to see if the install is working.
Logcat is located in the top menu under
Window- Show View - Other - Android - Logcat
Also try cleaning the project and restarting the emulator; and also, if the app doesn't show up when the emulator loads, try, without exiting the emulator, to run it again.

Are you using the latest studio? Seems like an old bug
Error when running emulator in Android Studio
Try waiting until the emulator boots, and then run the project.