I am having an error in creating TextViews by scheduling the application 'crash' on the screen
MainActivity.java
package com.example.matheus.login;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.NavigationView;
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.widget.LinearLayout;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
String login;
String senha;
String nome;
@Override
protected void onCreate(Bundle savedInstanceState) {
Bundle extras = getIntent().getExtras();
if(extras != null)
{
nome = extras.getString("nome");
}
super.onCreate(savedInstanceState);
setContentView(R.layout.content_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
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);
TextView text = (TextView)navigationView.getHeaderView(0).findViewById(R.id.nome);
text.setText(nome);
String[] textArray = {"One", "Two", "Three", "Four"};
DrawerLayout mFrame = (DrawerLayout) findViewById(R.id.container);
for( int i = 0; i < textArray.length; i++ )
{
TextView textView = new TextView(this);
textView.setText(String.valueOf(textArray[i]));
mFrame.addView(textView);
}
}
@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.
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
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) {
Intent intent = new Intent(MainActivity.this, MainActivity.class);
intent.putExtra("nome", nome);
MainActivity.this.startActivity(intent);
} else if (id == R.id.nav_gallery) {
Intent intent = new Intent(MainActivity.this, fechadas.class);
intent.putExtra("nome", nome);
MainActivity.this.startActivity(intent);
} else if (id == R.id.nav_share) {
Intent intent = new Intent(MainActivity.this, TelaLogin.class);
MainActivity.this.startActivity(intent);
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
content_main.xml (NavigationView)
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout 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"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.example.matheus.login.MainActivity"
tools:showIn="@layout/app_bar_main">
<LinearLayout
android:id="@+id/container"
android:layout_width="368dp"
android:layout_height="495dp"
tools:layout_editor_absoluteY="8dp"
tools:layout_editor_absoluteX="8dp"
android:orientation="vertical">
</LinearLayout>
</android.support.v4.widget.DrawerLayout>
Failed to crash
FATAL EXCEPTION: main
Process: com.example.rohwedder.login, PID: 15173
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.rohwedder.login/com.example.matheus.login.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.LinearLayout.addView(android.view.View)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.LinearLayout.addView(android.view.View)' on a null object reference
at com.example.matheus.login.MainActivity.onCreate(MainActivity.java:37)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
at com.example.matheus.login.MainActivity.onCreate(MainActivity.java:37)
, refers to this lineFrame.addView(textView);