How to Lock Activity in Android ?

In this example we are going to learn how we can lock screen's in android in portrait or landscape mode.

How to lock Activity in Android ? 

If you want lock activity first go to manifest file -> Then add 
android:screenOrientation="portrait" or android:screenOrientation="landscape" Mode 
in activity which you want to lock.

When you see some of the Game Application , those app by default open in landscape mode.



Lets see example...  

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:background="#ff0"

    android:orientation="vertical"

    tools:context="com.example.malik.blog.MainActivity">

    <TextView

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_marginTop="30dp"

        android:background="#612"

        android:gravity="center"

        android:padding="10dp"

        android:text="Portrait Mode"

        android:textColor="#f00"

        android:textSize="35sp"

        />

</LinearLayout>

MainActivity.java

package com.example.malik.blog;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }

}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.example.malik.blog">

    <application

        android:allowBackup="true"

        android:icon="@mipmap/ic_launcher"

        android:label="@string/app_name"

        android:roundIcon="@mipmap/ic_launcher_round"

        android:supportsRtl="true"

        android:theme="@style/AppTheme">

        <activity

            android:name=".MainActivity"

            android:screenOrientation="portrait">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

</manifest>

build.gradle

apply plugin: 'com.android.application'

android {

    compileSdkVersion 25

    buildToolsVersion "25.0.2"

    defaultConfig {

        applicationId "com.example.malik.blog"

        minSdkVersion 18

        targetSdkVersion 25

        versionCode 1

        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }

    buildTypes {

        release {

            minifyEnabled false

            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

        }

    }

}

dependencies {

    compile fileTree(dir: 'libs', include: ['*.jar'])

    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {

        exclude group: 'com.android.support', module: 'support-annotations'

    })

    compile 'com.android.support:appcompat-v7:25.3.1'

    compile 'com.android.support.constraint:constraint-layout:1.0.2'

    testCompile 'junit:junit:4.12'

}