Step 4: menu events, common la S, radiobutton, checkbox usage, and toast usage

About menu events

When you click the menu button, oncreateoptionsmenu (menu) is called );

You can override the public Boolean oncreateoptionsmenu (menu) {} event.

For example:

Public Boolean oncreateoptionsmenu (menu ){

// Operate menu to add menu items

// The first parameter is the group ID of the menu.

// The second parameter is the ID of the current menu (similar to setting the item subscript)

// The third parameter is its sorting (not understood for the moment)

// The fourth parameter is the text of the button.

Menu. Add (0, 1, 1, R. String. Exit );

Menu. Add (0, 2, 2, R. String. About );

Return super. oncreatoptionsmenu (menu );

}

 

Menu event: When you click an item in the menu, onoptionsitemselected (menutitem item) is automatically called );

Override public Boolean onoptionsitemseleted (menuitem item) {} event

Example: (Continued example)

Public Boolean onoptionsitemseleted (menuitem item ){

// Obtain the ID of the item clicked by the user and execute the corresponding event

If (item. getitemid () = 1 ){

Finish (); // end the current activity (content in the previous chapter)

}

Return super. onoptionsitemselected (item );

}

 

Common Layout: the XML layout type of Android is similar to the CSS layout, and many CSS-like styles can be used for layout.

Android font size unit uses PT, such as Android: textsize = "35pt"; distance uses dip instead of PX, such as Android: padding = "10dip"; // better compatibility than PX pixels

Padding-padding margin-margin. If both controls have margin, the distance between the two controls is the addition of the margin values of the two controls.

 

Absolute layout:

Linearlayout and tablelayout are usually nested for layout. Pay attention to the use of Android: Orientation = ""; // you can specify whether the layout is horizontal or vertical.

Common attributes:

Android: grimace // specifies the control position, such as center and right (Note: Alignment of the control content with this attribute)

Android: sigleline // if it is true, the control content is displayed in the same row

Android: layout_weight = "1" // This attribute is very important. In multi-layer nesting, you need to set this attribute, which means a few points of each.

 

Relative layout:

Common attributes:

Basic Words:

Above/above

Below // below

Left // left

Right // right

The following attributes use "*" instead of the above four words. Basically, each attribute has these four directions, so they all have similar results.

// The following attributes are used in the "separation relationship". For example, a and B can only be "tangent" recently"

Android: Layout _ * // place the control with this attribute on the * plane of the control with the specified ID. (Note: This attribute does not mean that the two controls must be completely pasted together. If there is a little bit of contact, this attribute is satisfied)

For example, a control has this property -- Android: layout_above = "@ ID/B"; that is, a control is on top of B.

 

 

Basic Words:

Top // above

Bottom // below

Left // left

Right // right

Similarly, "*" is used to replace the four words.

// The following attributes are used in "inclusion relationship", for example, a contains B;

Android: layout_align * // associate the edge of the control that owns this property with the edge of the control of the specified ID, A small one contains a small one)

For example, control a has this property --- Android: layout_alignleft = "@ ID/B"; this means that the left edge of control a is aligned with that of control B.

 

// The following attribute uses the same word as the previous one.

Android: layout_alignparent * // if the property is true, the control is aligned with its parent control *

For example, the control has this property --- Android: layout_alignleft = "true"; this means that the alignleft of the a control is left aligned in the parent control.

 

 

Basic Words:

Horizontal // horizontal

Inparent // horizontal and vertical

Vertical // vertical

// Use "*" to replace the above three words

Android: layout_center * // if this attribute is true, the control is placed in the center of * of the parent control.

For example, control a has this property-Android: layout_centerhorizontal = "true"; meaning that control a is placed in the horizontal center of the parent control (horizontally centered)

 

 

How to Use radiobutton:

In use, like other controls, you need to add radiobutton in XML, but each group of radiobutton needs to be separated by radiogroup.

For example, a group of single-choice buttons-Male & female

<Radiogroup

Android: Id = "@ + ID/gendergroup"

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: Orientation = "vertical" // determines whether the button is arranged horizontally or in the center.

>

<Radiobutton

Android: Id = "@ + ID/femalebutton"

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: text = "female"

/>

<Radiobutton

Android: Id = "@ + ID/malebutton"

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: text = "male"

/>

<Radiogroup>

 

Like other controls, you must use findviewbyid to obtain the radiogroup and all radiobutton contained in it;

When binding a listener, you need to use radiogroup to bind the listener. For example:

Gendergroup = (radiogroup) findviewbyid (R. Id. gendergroup );

Gendergroup. setoncheckedchangelistener ();

Listener interface: radiogroup. oncheckedchangelistener {}

Method of rewriting interface and click event of corresponding user:

Public void oncheckedchanged (radiogroup group, int checkedid ){

If (famalebutton. GETID () = checkedid ){

// Corresponding "when a user clicks the male button" Event

}

Else if (malebutton. GETID () = checkedid ){

// Corresponding "User click female" Event

}

}

 

 

Checkbox usage:

Similarly, the layout in XML is as follows:

<Checkbox

Android: Id = "@ + ID/run"

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: text = "running"

/>

Runbox = (checkbox) findviewbyid (R. Id. Run );

Event binding: runbox. setoncheckedchangelistener ();

Listener type: compoundbutton. oncheckedchangelistener {}; // Note: You need to rewrite the corresponding event for each checkbox. Do not know if the existence of the listener does not respond to a set of checkboxes? Let's look back later.

Because each checkbox needs to be rewritten once, you can use a temporary variable to override it;

For example:

Runbox. setoncheckedchangelistener (New compoundbutton. oncheckedchangelistener {

Public void oncheckedchanged (compoundbutton buttonview, Boolean ischecked ){

If (ischecked ){

// Respond to the "user checked the 'run' checkbox" Event

}

Else {

// The user does not select

}

} // End for oncheckedchanged

} // End for checkbox listener Interface

); // End for control to bind the listener. Remember not to miss ";". It is best to finish setoncheckedchangelistener () first, and then plan to use the new interface in the slogan.

 

 

 

Toast usage // similar to the message on the object-oriented writing interface, the user prompts the user some errors, it seems that the button cannot be added? Coming back later

// The first parameter is the activity that owns the toast. Assume that the activity that owns the toast is called "test", and test. This indicates the activity object test.

// The second parameter is the text in the toast, that is, the content to be displayed.

// How is the third parameter displayed? Or? It's a constant. Let's use it like this. I'll see other usage later.

Toast. maketext (text. This, "hello", Toast. length_short );