MainActivity.java

package com.rakuishi.share;

import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

public class MainActivity extends ActionBarActivity {

    private final String[] packages = {"com.twitter.android", "com.facebook.katana", "jp.naver.line.android"};
    private final int TWITTER = 0;
    private final int FACEBOOK = 1;
    private final int LINE = 2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.button_twitter).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (isAlreadyInstalled(TWITTER)) {
                    Intent intent = new Intent();
                    intent.setAction(Intent.ACTION_SEND);
                    intent.setPackage(packages[TWITTER]);
                    intent.setType("text/plain");
                    intent.putExtra(Intent.EXTRA_TEXT, "Twitter");
                    startActivity(intent);
                } else {
                    shareAppDownload(TWITTER);
                }
            }
        });

        findViewById(R.id.button_facebook).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (isAlreadyInstalled(FACEBOOK)) {
                    Intent intent = new Intent();
                    intent.setAction(Intent.ACTION_SEND);
                    intent.setPackage(packages[FACEBOOK]);
                    intent.setType("text/plain");
                    intent.putExtra(Intent.EXTRA_TEXT, "http://rakuishi.com/");
                    startActivity(intent);
                } else {
                    shareAppDownload(FACEBOOK);
                }
            }
        });

        findViewById(R.id.button_line).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (isAlreadyInstalled(LINE)) {
                    Intent intent = new Intent();
                    intent.setAction(Intent.ACTION_VIEW);
                    intent.setData(Uri.parse("line://msg/text/" + "LINE"));
                    startActivity(intent);
                } else {
                    shareAppDownload(LINE);
                }
            }
        });
    }

    private Boolean isAlreadyInstalled(int id) {
        try {
            PackageManager packageManager = getPackageManager();
            packageManager.getApplicationInfo(packages[id], PackageManager.GET_META_DATA);
            return true;
        } catch (PackageManager.NameNotFoundException e) {
            return false;
        }
    }

    private void shareAppDownload(int id) {
        Uri uri = Uri.parse("market://details?id=" + packages[id]);
        startActivity(new Intent(Intent.ACTION_VIEW, uri));
    }
}