Boost Android Development Skills To Produce Quality Apps

1// To create activity, a class must extend Activity or AppCompatActivity class
2 // AppCompatActivity is used to support ActionBar and design features for older version
3public class MainActivity extends AppCompatActivity {
4
5    @Override
6    protected void onCreate(Bundle savedInstanceState) {
7        super.onCreate(savedInstanceState);
8        // static view for MainActivity
9        setContentView(R.layout.activity_main);
10    }
11}

1public class MainActivity extends AppCompatActivity {
2
3	 // called only once when activity is created
4	 // so optimal place to initialize GUI component and services
5	 @Override
6     protected void onCreate(Bundle savedInstanceState){...};
7
8 	// called everytime when user comes to this activity
9	 @Override
10     protected void onStart(){...};
11
12 	// called when activity is completely visible
13	 @Override
14     protected void onResume(){...};
15
16 	// called when activity is partially visible
17 	// covered by some dialog
18	 @Override
19     protected void onPause(){...};
20
21     // called when current activity is covered by another activity
22     // when user go to next activity
23     protected void onStop(){...};
24
25 	// called when activity's object is destroyed and no longer accessible
26 	// when user press back-press button
27	 @Override
28     protected void onDestroy(){...};
29 }

1<?xml version="1.0" encoding="utf-8"?>
2<manifest xmlns:android="http://schemas.android.com/apk/res/android"
3	package="com.pavneet.android.boost">
4
5 	<!--needs to be added to get access to Internet -->
6	<uses-permission android:name="android.permission.INTERNET"/>
7
8    <application
9 	  <!--app icon-->
10        android:icon="@mipmap/ic_launcher"
11 	  <!--app name-->
12        android:label="@string/app_name"
13 	  <!--aa-->
14        android:roundIcon="@mipmap/ic_launcher_round"
15 	  <!--support for right to left languages-->
16        android:supportsRtl="true"
17 	  <!--XML based theme file-->
18        android:theme="@style/AppTheme">
19
20    <!--Register Activity, declare this activity as launcher using intent-filter
21    mean first activity to be opened, on click of app icon-->
22        <activity android:name=".MainActivity">
23            <intent-filter>
24                <action android:name="android.intent.action.MAIN" />
25
26                <category android:name="android.intent.category.LAUNCHER" />
27            </intent-filter>
28        </activity>
29
30        <activity android:name=".AnotherDefaultActivityYetToBeCreated"/>
31
32    </application>
33
34 </manifest>

1package com.pavneet.android.boost;
2
3import android.os.Bundle;
4import android.support.design.widget.FloatingActionButton;
5import android.support.design.widget.Snackbar;
6import android.support.v7.app.AppCompatActivity;
7import android.support.v7.widget.Toolbar;
8import android.view.View;
9
10public class FoatingAndSnakBarActivity extends AppCompatActivity {
11
12    @Override
13    protected void onCreate(Bundle savedInstanceState) {
14        super.onCreate(savedInstanceState);
15        setContentView(R.layout.activity_foating_and_snak_bar);
16
17        FloatingActionButton fab = findViewById(R.id.fab);
18        fab.setOnClickListener(new View.OnClickListener() {
19            @Override
20            public void onClick(View view) {
21                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
22                        .setAction("Action", new View.OnClickListener() {
23                            @Override
24                            public void onClick(View view) {
25                                // sncakbar button clicked
26                            }
27                        }).show();
28            }
29        });
30    }
31}

1<?xml version="1.0" encoding="utf-8"?>
2<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
3    xmlns:app="http://schemas.android.com/apk/res-auto"
4    xmlns:tools="http://schemas.android.com/tools"
5    android:layout_width="match_parent"
6    android:layout_height="match_parent"
7    tools:context="com.pavneet.android.boost.FoatingAndSnakBarActivity">
8
9
10    <android.support.design.widget.FloatingActionButton
11        android:id="@+id/fab"
12        android:layout_width="wrap_content"
13        android:layout_height="wrap_content"
14        android:layout_gravity="bottom|end"
15        android:layout_margin="@dimen/fab_margin"
16        app:srcCompat="@android:drawable/ic_dialog_email" />
17
18</android.support.design.widget.CoordinatorLayout>

1<android.support.design.widget.TextInputLayout
2        android:layout_width="match_parent"
3        android:layout_height="wrap_content">
4
5    <android.support.design.widget.TextInputEditText
6            android:layout_width="match_parent"
7            android:layout_height="wrap_content"
8            android:hint="@string/form_username"/>
9
10</android.support.design.widget.TextInputLayout>

1startActivity(new Intent(YourCurrentActivity.this,DestinationActivity.class));
2// animate by applying fade in and fade out animations
3overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);

1// fetch the image as bitmap
2Bitmap b= BitmapFactory.decodeResource(getResources(),R.drawable.norml);
3// create a rounded drawable
4RoundedBitmapDrawable drawable= RoundedBitmapDrawableFactory.create(getResources(),b);
5// create a circular image
6drawable.setCircular(true);

1<?xml version="1.0" encoding="utf-8"?>
2<LinearLayout android:layout_height="match_parent"
3    android:layout_width="match_parent"
4    xmlns:android="http://schemas.android.com/apk/res/android" >
5
6    <View
7        android:background="#c44cd4"
8        android:layout_width="0dp"
9        android:layout_weight="1"
10        android:layout_height="match_parent"/>
11    <View
12        android:layout_weight="1"
13        android:background="#7bf2dc"
14        android:layout_width="0dp"
15        android:layout_height="match_parent"/>
16</LinearLayout>

1onView(withId(R.id._button)).perform(click()); // perform click
2onView(withText("Hello")).check(matches(isDisplayed())); // check a view is visible with text "Hello"

1public class MainActivity extends AppCompatActivity
2{
3    private ArrayAdapter<String> adapter;
4    private ListView listView;
5
6    protected void onCreate(Bundle paramBundle)
7    {
8        super.onCreate(paramBundle);
9        setContentView(2130968605);
10        this.listView = ((ListView)findViewById(2131558552));
11        this.adapter = new ArrayAdapter(this, 17367046, Util.DEMO_LIST_ITEMS);
12        this.listView.setAdapter(this.adapter);
13    }
14}

1import android.support.v7.a.a;
2import android.support.v7.a.s;
3import android.support.v7.a.u;
4
5public class MainActivity extends s
6{
7    private ListView i;
8    private ArrayAdapter<String> l;
9
10    protected void onCreate(Bundle paramBundle)
11    {
12        super.onCreate(paramBundle);
13        setContentView(2130968602);
14        this.i = ((ListView)findViewById(2131558552));
15        this.l = new ArrayAdapter(this, 17367046, Util.DEMO_LIST_ITEMS);
16        this.i.setAdapter(this.l);
17    }
18}

1android {
2    compileSdkVersion 26
3    buildToolsVersion "26.0.1"
4    defaultConfig {
5        applicationId "com.pavneet.android.boost"
6        minSdkVersion 15
7        targetSdkVersion 26
8        versionCode 1
9        versionName "1.0"
10        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
11    }
12    buildTypes {
13        debug {
14            minifyEnabled true
15            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
16        }
17        release {
18            minifyEnabled true
19            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
20        }
21    }
22}

1if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
2	// current os is marshmallow or above
3}else{/* perform alternative actions for older version */}

1Picasso.with(context)
2  .load(url)
3  .resize(50, 50)
4  .centerCrop()
5  .into(imageView)