Basic use of ToolBar and custom ToolBar

First layout file activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="cainiaoshop.com.toolbar.MainActivity">                    

    <android.support.v7.widget.Toolbar
android:id="@+id/toolBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?attr/colorPrimary"
app:title="laiba"
app:navigationIcon="@mipmap/back"
>                                                        

    </android.support.v7.widget.Toolbar>
</RelativeLayout>

menu file:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
>        
<item android:id="@+id/action_settings" android:title="@string/action_settings"
android:orderInCategory="100" app:showAsAction="never"
/>        
    <item android:id="@+id/action_menu" android:title="@string/action_menu"
android:orderInCategory="100" app:showAsAction="never"
/>                
    <item android:id="@+id/action_mine" android:title="@string/action_mine"
android:orderInCategory="100" app:showAsAction="never"
/>                
</menu>

Resource file string.xml

<resources>
    <string name="app_name">ToolBar</string>
    <string name="action_settings">settings</string>
    <string name="action_menu">menu</string>
    <string name="action_mine">mine</string>


</resources>

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private Toolbar toolBar;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        toolBar= (Toolbar) findViewById(R.id.toolBar);
        toolBar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this,"onclick",Toast.LENGTH_SHORT).show();
                finish();
            }
        });
        toolBar.inflateMenu(R.menu.main);
        toolBar.setOnMenuItemClickListener(new Toolbar.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem item) {
                int id=item.getItemId();
                if(id==R.id.action_settings){
                    Toast.makeText(MainActivity.this,"action_settings",Toast.LENGTH_SHORT).show();
                }
                if(id==R.id.action_menu){
                    Toast.makeText(MainActivity.this,"action_menu",Toast.LENGTH_SHORT).show();
                }
                if(id==R.id.action_mine){
                    Toast.makeText(MainActivity.this,"action_mine",Toast.LENGTH_SHORT).show();
                }
                return false;
            }
        });
    }
}