Piglet's Android Getting Started Day 2

Piglet's Android Getting Started Day 2

Android Interface Development First Experience

Introduction to this section:

In the previous section, we have a preliminary understanding of the Android system features and platform architecture;

Learned to use Eclipse or Android studio to build Android development environment, familiar with the corresponding IDE development process;

and the corresponding engineering catalogue; Some relevant nouns, aapt,dx, etc.; some of the ADB directives commonly used by the command line;

App packaging, compiling, and running processes! In this section we will experience the development of the Android interface!

Learn six layouts, get a basic understanding of Android's four components, and the lifecycle of your app, build a phone dialer, and much more!

Don't say much nonsense!

Body:

Learning Roadmap for this section:

Learning route Analysis:

① understand what the four components and intent of Android are, what to do with them! In the following chapters, we will explain in detail

② Learn about the app life cycle: five states

③ in-depth analysis of HelloWorld's engineering catalogue

④ familiar with six layout methods

⑤ familiar with three ways of prompting: status bar, dialog box and toast

Complete implementation of ⑥ telephone dialer

⑦9patch (9 sister) use: Make Scalable pictures!

Android four major components and intent initial analysis:

the life cycle of the app (app):

Attention:

Unlike other smartphone operating systems :The app's life cycle (survival time) is not controlled by the process itself ;

It is determined by the Android system , and the main factor of the impact: the importance of the process to the user , as well as what remains in the current system

available memory space; When there is not enough memory available, some processes are terminated to reclaim memory resources!

Process level diagram:

Learn more about the app's Engineering catalog:1. References to resources:

2. Detailed code parsing in the engineering catalogue:

Three important documents: Portal

user Interface Development First experience:

Before we create our world, we need to know something first:

1.View class : Is the parent class for all visual controls , providing a description of the component and a time-processing method

2.ViewGroup class : Can have child controls, can be considered as containers

3. Commonly visible Android apps are made up of visual controls + layouts! The properties of the control can be

Statically set in XML or dynamically in Java code

Well, then we're going to start creating the layout of our Phone Dialer:

There are two ways to do this:① Drag components ② write their own code

The author prefers the latter, because the code for drag generation has some redundancy

The code is as follows:

Main.xml:

<linearlayout  xmlns:android= "http://schemas.android.com/apk/res/android"    xmlns:tools= "http// Schemas.android.com/tools "    android:id=" @+id/linearlayout1 "    android:layout_width=" Match_parent    " android:layout_height= "Match_parent"    android:orientation= "vertical"    tools:context= ". MyActivity "    >    <textview        android:layout_width=" wrap_content "        android:layout_height=" wrap _content "        android:text=" @string/input_num "/>    <edittext        android:layout_width=" match_parent "        android:layout_height=" wrap_content "        android:id=" @+id/editnum "/>    <button        android: Layout_width= "Wrap_content"        android:layout_height= "wrap_content"        android:text= "@string/btn_call"        android:id= "@+id/btncall"/></linearlayout>

Code parsing:

is to define a linearlayout (linear layout) and set the arrangement direction to vertical, that is, one line to place a component;

Then we define TextView (text label), EditText (input box), button (buttons), very simple

the six major layouts of Android

linearlayout: Linear layout

Link:android---linearlayout (linear layout) detailed

relativelayout: Relative layout

Link:android---relativelayout (relative layout) detailed

framelayout: Frame layout

Link:android---framelayout (frame layout) detailed

tablelayout: Table layout

Link:android---tablelayout (table layout) detailed

absolutelayout: Absolute Layout

Links:android---absolutelayout (absolute layout) detailed

GridLayout: Grid layout

Links:Android---GridLayout (Grid layout) detailed

Summary of layout usage:

The common usage is to use LinearLayout's Weight property +relativelayout (relative layout) for layout, as this can

Solve the adaptive problem of the screen

The so-called adaptive problem is that one of your interfaces is centered on a cell phone, but the components get messed up when you change a phone, or stretch

Deformation and so on! Of course other layouts are also necessary to learn!!!

three ways to prompt:dialog box: alertdialog:

Link: Parent class for dialog box (alertdialog)

toast(toast) and Notification(status bar)

Links: Toast and notification

complete implementation of the Phone Dialer:

On the basis of the previous Main.xml layout, after adding some code in the mainactivity:

Package Example.jay.com.myfirstapplication;import Android.app.activity;import Android.content.intent;import Android.net.uri;import Android.os.bundle;import Android.view.view;import Android.widget.button;import    Android.widget.edittext;public class MyActivity extends Activity {private EditText editnum;    Private Button Btncall;        @Override protected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate);        Setcontentview (r.layout.activity_my);        ① Component Instantiation Editnum = (EditText) Findviewbyid (r.id.editnum);        Btncall = (Button) Findviewbyid (R.id.btncall); Set Click events for the Dial button: Btncall.setonclicklistener (new View.onclicklistener () {@Override public void                OnClick (View v) {//Gets the number value in the edit box: String mobile = Editnum.gettext (). toString ();                Intent it = new Intent ();     Add a behavior for intent: Make a call and write the phone number to the IT it.setaction ("Android.intent.action.CALL");           It.setdata (Uri.parse ("Tel:" +mobile));            Start another activity startactivity (it);    }        }); }}

Code parsing:Here we set a click event for the button, and when we click the button, get the phone number in the input boxthrough intent intent, tell the system, who am I going to call,call, and then write the phone number intent, start intent, finish

Run:

We need to start a separate virtual machine:

Virtual Machine 5556 has a phone dialed in!

Nine sister: Use of 9patch tools:

Make scalable, proprietary images,. 9.png Images:

Link: Make a partially stretched picture material