In Android development, to use the ToolBar control to replace the ActionBar control, you need to use the setSupportActionBar() method in the java code, as follows:

1 Toolbar toolbar = (Toolbar) this.findViewById(R.id.toolBar);
2 this.setSupportActionBar(toolbar);

There are two common types of errors:

1. Method parameter error

This kind of error is because the wrong class is imported, put the following code

1 import android.widget.Toolbar;

Replace with the following code

1 import android.support.v7.widget.Toolbar;

2. Method name error

Need to inherit ActionBarActivity class or AppCompatActivity class.

Because the ActionBarActivity class is obsolete, it is recommended to inherit the AppCompatActivity class.

Note: If you inherit the AppCompatActivity class, you need to use the Theme.AppCompat.Light.NoActionBar theme, for example

<style name="AppTheme.Base" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="android:windowNoTitle">true</item>
        <item name="android:windowActionBar">false</item>
</style>

Similar Posts:

• Error:This Activity already has an action bar supplied by the window decor.
• Actionbar expiration problem
• classes could not be found: – android.support.v7.i
• [Solved] Android Studio Warning: Failed to load AppCompat ActionBar with unknown error
• [Solved] error: resource style/AppTheme (aka com.example.myapplication:style/AppTheme
• The image set by app: srccompat in Android constraintlayout cannot be displayed
• The Android studio preview interface reports an error render problem
• [Solved] Theme Error retrieving parent for item: No resource found that matche
• Can’t find it“ android:Theme.Holo.Light.DarkActionBar ” [How to Solove]
• Warning: Each child in an array or iterator should have a unique “key” prop. Check the render method