Javascript, CSS, HTML and REST of web development: Android app development quick start

Saturday, June 11, 2016

Android app development quick start

I've been diving into native Android application development with Android Studio lately. It went quite well, thanks to lots of available tutorials and large community on Stackoverflow.

As a result of last 2 weeks I've created this gist with links and code snippets for Android development that will hopefully help you to bootstrap.

Full gist is inside of the post.

UI

Showing Toast

  Button linkBtn = (Button) findViewById(R.id.button_toast);
        linkBtn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Toast.makeText(GolfcourseDetailActivity.this, "Here's your toast!",
                        Toast.LENGTH_LONG).show();
            }
        });

tutorial link

Showing alert

builder = new AlertDialog.Builder(this);
//Setting message manually and performing action on button click
builder.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int id) {
        //seems to close the app!!
        finish();
    }
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int id) {
        //  Action for 'NO' Button
        dialog.cancel();
    }
});

 AlertDialog alert = builder.create();
//Setting the title manually
//alert.setTitle(title);
//alert.setMessage(message);
alert.show();

Set background of the element in a View

attribute: android:background="@drawable/ID_OF_IMAGE"

Use string value from resources in Java `R.string.app_name`s

Activity set title:

in XML - android:label="@strings/my_activity_label"
in JAVA - setTitle("Hello StackOverflow");

1.3) How to add image to view

Using drawables; first declare in res/drawables, then use in layout:

```
<ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/imageView"
        android:layout_centerHorizontal="true"
        android:src="@drawable/ID_OF_THE_DRAWABLE"/>
        ```

1.4) Show back button in the bar

```
getActionBar().setDisplayHomeAsUpEnabled(true);
```

1.5) Show HTML page in the Activity

Add html/css to assets, then use it in the activity:

	WebView myWebView = (WebView) findViewById(R.id.webview);
	myWebView.loadUrl("file:///android_asset/components_webpage.html");

"However the TextView is referenced, it will be filled with the toString() of each object in the array. You can add lists or arrays of custom objects. Override the toString() method of your objects to determine what text will be displayed for the item in the list."

1.6) Content lists

You need ArrayAdapter and custom data type Class, see How to use ArrayAdapter
Then reasoning from here - theopentutorials.com

1.7) Open another activity by click on the button

In Java class:

    public void openListActivity (View v) {
        Intent intent = new Intent(this, MY_ACTIVITY_CLASS_NAME.class);
        startActivity(intent);
    }

then in the layout XML:

<Button
	android:layout_width="wrap_content"
	android:layout_height="wrap_content"
	android:text="Back to list"
	android:id="@+id/button3"
	android:onClick="openListActivity"
	android:layout_alignParentBottom="true"
	android:layout_centerHorizontal="true" />

Build/DEV process

see: build.gradle
Gradle and build process
Put messages to log:

Log.d("MY_ACTIVITY_NAME", "opening state...");

How to open link in a browser

In Java class

private void goToUrl (String url) {
     Uri uriUrl = Uri.parse(url);
     Intent launchBrowser = new Intent(Intent.ACTION_VIEW, uriUrl);
     startActivity(launchBrowser);
 }
 private void goToSu () {
     String addres = "http://stackoverflow.com/";
     goToUrl(addres);
 }
 ```

then in layout template:

```

5) Network

How to call json API in JAVA - Android app Volley or Retrofit

How to store data

Use SQLite, then inspect change though ADM
Use SharedPreferences (get/set via Editor)

SharedPreferences pref = getApplicationContext().getSharedPreferences(SAVE_PREF_ID, MODE_PRIVATE);
SharedPreferences.Editor sp = pref.edit();
sp.putString(SAVE_KEY_NAME, title);
//..
sp.apply();

7) General

API levels
Styles generator
Make activity as a default, add to Maniseft file, in selected activity definition

<intent-filter>
	<action android:name="android.intent.action.MAIN" />
	<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>

8) Sample apps

9) Tutorials and videos