I am working on socket programming. I am new to it. My application of socket programming works well in android 10 but when I try it with android 5.1 when I start communication from socket it crashes its working well in android 10

here is my code //mainactivity

package com.androidbegin.socket_programming;

import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import java.net.Socket;

public class MainActivity extends AppCompatActivity{

public TextView messageFromServer;
public int packet_length;
public int track_id;
public int speed;
public int azimuth;
public int heading;
public int iff_status;
public int wco;
public int range;
public int height;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    messageFromServer = (TextView) findViewById(R.id.from_server);
    thread.start();


}




    final Handler handler = new Handler();
    Thread thread = new Thread(new Runnable() {
            @RequiresApi(api = Build.VERSION_CODES.O)
            @Override
            public void run () {

            while(true) {

                try {
                    Socket s = new Socket("192.168.126.188", 8054);

                    DataInputStream input=new DataInputStream(s.getInputStream());
                    byte[] bytes=new byte[15];


                    while((len = input.read(bytes)) != -1)
                    {
                         input.read(bytes);
                         packet_length=Byte.toUnsignedInt(bytes[0]);
                         track_id=Byte.toUnsignedInt(bytes[1]);
                         range=256*Byte.toUnsignedInt(bytes[2])*256 256*Byte.toUnsignedInt(bytes[3]) Byte.toUnsignedInt(bytes[4]);
                         height=256*Byte.toUnsignedInt(bytes[5]) Byte.toUnsignedInt(bytes[6]);
                         azimuth=256*Byte.toUnsignedInt(bytes[7]) Byte.toUnsignedInt(bytes[8]);
                         heading=256*Byte.toUnsignedInt(bytes[9]) Byte.toUnsignedInt(bytes[10]);
                         speed=256*Byte.toUnsignedInt(bytes[11]) Byte.toUnsignedInt(bytes[12]);
                         iff_status=bytes[13];
                         wco=bytes[14];


                        printValues();

                  
                    handler.post(new Runnable() {
                        @Override
                        public void run() {
                      }
                    });

                    }

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    });
    public void printValues()
    {
        messageFromServer.setText(range " " height " " azimuth " " heading " " speed " " iff_status " " wco);
    }

}

code from build.gradle app file

plugins {
id 'com.android.application'
}

android {
compileSdk 31

defaultConfig {
    applicationId "com.androidbegin.socket_programming"
    minSdk 21
    targetSdk 31
    versionCode 1
    versionName "1.0"

    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
}
compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}
}

dependencies {

implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4. '
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

}

I need help with this. I don't know why its crashes

CodePudding user response：

I think you've chosen Android 10 in options menu. When you create a new project, you have to chose the minimum android version for your android app. And, you can use Kotlin also.

CodePudding user response：

my suggestion is to set the minimum SDK to 23