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This article mainly explains "how to implement ActionBar in Android". The explanation content in this article is simple and clear, easy to learn and understand. Please follow the ideas of Xiaobian slowly and deeply to study and learn "how to implement ActionBar in Android" together!

There are two ways to create it.

Created with java code

Defined in XML file

The first method:

import android.graphics.Color; import android.support.v7.app.AppCompaActivity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.view.SubMenu;import android.widget.EditText;import android.widget.Toast;public class MainActivity extends AppCompaActivity { //Define the label for the Font Size menu item final int FONT_10 = 0X111; final int FONT_12 = 0X112; final int FONT_14 = 0X113; final int FONT_16 = 0X114; final int FONT_18 = 0X115; //define the label of "General menu item" final int PLAIN_ITEM = 0x11b; //define the label of "Font color" menu item final int FONT_RED = 0X116; final int FONT_BLUE = 0X117; final int FONT_GREEN = 0X118; private EditText editText; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); editText = (EditText) findViewById(R.id.edit); } //Trigger this method when the user clicks the menu key @Override public boolean onCreateOptionsMenu(Menu menu) {// Add "font size" submenu to menu SubfontMenu = menu.addSubMenu("font size");// Settings menu icon fontMenu.setIcon(R.mipmap.ic_launcher);// Set icons for menu headers fontMenu.setHeaderIcon(R.mipmap.ic_launcher_round);// Set the title of the menu header fontMenu.setHeaderTitle("Select font size"); fontMenu.add(0, FONT_10, 0, "10 point font"); fontMenu.add(0, FONT_12, 0, "12 point font"); fontMenu.add(0, FONT_14, 0, "14 point font"); fontMenu.add(0, FONT_16, 0, "16 point font"); fontMenu.add(0, FONT_18, 0, "font 18");// Add "general menu item" to menu menu.add(0, PLAIN_ITEM, Menu.NONE, "General menu items");// Add a submenu for font colors to the menu SubMenu colorMenu = menu.addSubMenu("Font Color"); colorMenu.setIcon(R.color.colorPrimaryDark);// Set icons for menu headers colorMenu.setHeaderIcon(R.color.colorAccent);// Set the title of the menu header colorMenu.setHeaderTitle("Select text color"); colorMenu.add(0, FONT_RED, 0, "RED"); colorMenu.add(0, FONT_GREEN, 0, "GREEN"); colorMenu.add(0, FONT_BLUE, 0, "Blue"); return super.onCreateOptionsMenu(menu); }//Callback method after menu item of options menu is clicked @Override public boolean onOptionsItemSelected(MenuItem item) {// Determine which menu item you clicked switch (item.getItemId()) { case FONT_10: editText.setTextSize(10 * 2); break; case FONT_12: editText.setTextSize(12 * 2); break; case FONT_14: editText.setTextSize(14 * 2); break; case FONT_16: editText.setTextSize(16 * 2); break; case FONT_18: editText.setTextSize(18 * 2); break; case FONT_RED: editText.setTextColor(Color.RED); break; case FONT_GREEN: editText.setTextColor(Color.GREEN); break; case FONT_BLUE: editText.setTextColor(Color.BLUE); break; case PLAIN_ITEM: Toast.makeText(MainActivity.this, "You clicked the General Menu", Toast.LENGTH_SHORT).show(); break; } return true; }}

The onCreateOptionMenu() method is triggered when the user clicks on the menu key, so if you want to have your own implementation, you have to rewrite this method. This method passes in a menu object whose add() method adds submenus. Similarly, submenus can add menu items to themselves via the add() method.

The add() method has four parameters:

The first parameter is groupId, which can be used to control whether menu items are in the same group.

The second parameter is itemId, which is the Id of each menu item.

The third parameter is order, which controls the order of each item. If you don't care about order, you can pass NONE or 0. The lower the value of the int, the higher the order of menu items. For example, menu items with order=1 are higher than those with order=2.

The fourth parameter is title, which corresponds to the title of the menu item.

Each menu item corresponds to a series of setter methods, as the name implies.

If a menu item needs to have its own implementation when clicked, you must override the onOptionsItemSelected() method, which passes in the menuItem item that has already been created. Switch provides a different implementation for each menu item click event.

Java code to implement the various menu items may be more consistent with thinking habits, but often lead to bloated code.

Here's how to define an options menu in XML:

To define a menu in an XML file, you first need to create a folder called menu in the resource file;

Then create an xml file in it:

The root node of an xml file must be menu;

Each item tag defines a menu item, and you can create submenus by redefining them in.

Each item supports defining many attributes, the most important of which are id, icon, title and showAsAction;

The first three items are easy to understand, mainly showAsAction is more difficult to understand. The showAsAction value has five alternatives, and combinations are supported:

The copy code is as follows:

android:showAsAction=["ifRoom" | "never" | "withText" | "always" | "collapseActionView"]

Here is a concept to be clear:

The one shown above with a title and two buttons is called an ActionBar. It has been introduced since Android 3.0. ActionBar is used by default as a toolbar. Items in ActionBar can be displayed in two ways-buttons and overflow menus.

In other words, Android's menu is no longer a simple menu. It can be said to be part of ActionBar. It can also be said that the menu items can be displayed as buttons in ActionBar (by setting the value of showAsAction).

As shown below, two icons represent buttons, and three vertical dots represent overflow menus:

Anyway, about showAsAction values:

When it is ifRoom, it means that if there is space, it will be displayed. If both are defined as IfRoom in the code above, it will appear as two buttons.

"Never", as the name suggests, means not to display buttons. All concentrated in overflow menu.

"With Text" means that buttons follow text when displayed. However, the text is generally not displayed. If the user presses the button for a long time, the corresponding title will be displayed.

" Always" corresponds to "never." It is always displayed, so it is not necessary to use "always" as little as possible.

CollapseActionView belongs to the settings related to toolbar(equivalent to the upgraded version of ActionBar, more flexible in all aspects), which deviates from the topic of this article and will not be repeated.

Thank you for reading, the above is the content of "how to implement ActionBar in Android", after learning this article, I believe everyone has a deeper understanding of how to implement ActionBar in Android, and the specific use situation needs to be verified by practice. Here is, Xiaobian will push more articles related to knowledge points for everyone, welcome to pay attention!

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