Mohammadreza Mohammadreza - 5 months ago 45
Java Question

My application doesn't run itself MainActivity

I got some error in my logcat and my application doesn't run in my smartphone...
I changed some codes in my manifest and MainActivity (named as HomaActivity )

THIS IS MY MANIFEST:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="ir.homa">
<permission
android:name="android.permission.INTERNET">
</permission>
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="24" />
<application
android:name=".AppController"
android:allowBackup="true"
android:label="@string/app_name"
android:theme="@style/AppTheme" >



<activity
android:name=".HomaActivity"
android:label="@string/app_name"
android:launchMode="singleTop" >
<intent-filter >
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

<activity
android:name=".LoginActivity"
android:label="@string/app_name"
android:launchMode="singleTop"
android:windowSoftInputMode="adjustPan" >
<category android:name="android.intent.category.DEFAULT" />
</activity>
<activity
android:name=".RegisterActivity"
android:label="@string/app_name"
android:launchMode="singleTop"
android:windowSoftInputMode="adjustPan" >

<category android:name="android.intent.category.DEFAULT" />
</activity><!-- ATTENTION: This was auto-generated to add Google Play services to your project for
App Indexing. See https://g.co/AppIndexing/AndroidStudio for more information. -->
<meta-data
android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />


</application>

</manifest>


THIS IS HomaActivity.Java :

package ir.homa;

import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.NavigationView;
import android.support.design.widget.Snackbar;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;


public class HomaActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_homa);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();

NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);




}

/**
* Logging out the user. Will set isLoggedIn flag to false in shared
* preferences Clears the user data from sqlite users table
*/





@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.homa, 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);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();

if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {

} else if (id == R.id.nav_slideshow) {

} else if (id == R.id.nav_manage) {

} else if (id == R.id.nav_share) {

} else if (id == R.id.nav_send) {

}

DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
public GoogleApiClient client;
@Override
public void onStart() {
super.onStart();

// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
GoogleApiClient client = null;
client.connect();
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Homa Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://ir.homa/http/host/path")
);
AppIndex.AppIndexApi.start(client, viewAction);
}

@Override
public void onStop() {
super.onStop();

// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Homa Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://ir.homa/http/host/path")
);
AppIndex.AppIndexApi.end(client, viewAction);
client.disconnect();
}
}


THESE ARE ERRORS IN MY LOGCAT:

07-02 20:26:44.441 26501-26501/ir.homa E/AndroidRuntime: FATAL EXCEPTION: main
Process: ir.homa, PID: 26501
java.lang.RuntimeException: Unable to start activity ComponentInfo{ir.homa/ir.homa.HomaActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.common.api.GoogleApiClient.connect()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2658)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5832)
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:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.common.api.GoogleApiClient.connect()' on a null object reference
at ir.homa.HomaActivity.onStart(HomaActivity.java:127)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1234)
at android.app.Activity.performStart(Activity.java:6258)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2621)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723) 
at android.app.ActivityThread.access$900(ActivityThread.java:172) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:145) 
at android.app.ActivityThread.main(ActivityThread.java:5832) 
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:1399) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194) 

Answer

This is your problem, you're calling a method on a null variable:

GoogleApiClient client = null;
client.connect();

you need to initialize the client first. something like this

GoogleApiClient googleApiClient = new GoogleApiClient.Builder(this)
    .enableAutoManage(this /* FragmentActivity */,
                  this /* OnConnectionFailedListener */)
    .addApi(Drive.API)
    .addScope(Drive.SCOPE_FILE)
    .build();

Check this link.