Make aide project

MainActivity.java code

package ucsmb.apkph.com.phonecall;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Build;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

TextView tv;

String phno = "";

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

    //permission request
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (checkCallingOrSelfPermission(Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.CALL_PHONE}, 0);
        }
    }
    phno = "";
    tv = findViewById(R.id.phoneNum);
    tv.setText("");
}

public void clickNum(View v) {
    Button btn = (Button) v;
    phno += btn.getText();
    tv.setText(phno);
}

public void del(View v) {
    if (!phno.equals("")) {
        phno = phno.substring(0, phno.length() - 1);
        tv.setText(phno);
    }
}

public void call(View v) {
    Intent callIntent = new Intent(Intent.ACTION_CALL);
    callIntent.setData(Uri.parse("tel:" + phno.replace("#", "%23")));
    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {
        return;
    }
    startActivity(callIntent);
}

}
manifast
########

<uses-permission android:name="android.permission.CALL_PHONE" />
<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">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

########

activity_main.xml

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="right"
    android:layout_marginRight="8dp"
    android:layout_marginTop="8dp"
    android:onClick="del"
    android:text="DEL" />

<TextView
    android:id="@+id/phoneNum"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="0945"
    android:textColor="@android:color/black"
    android:textSize="30dp" />

<GridLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:columnCount="3">

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="1"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="2"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="3"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="4"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="5"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="6"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="7"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="8"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="9"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="*"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="0"
        android:textSize="30dp" />

    <Button
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:onClick="clickNum"
        android:text="#"
        android:textSize="30dp" />
</GridLayout>

<Button
    android:layout_width="80dp"
    android:layout_height="80dp"
    android:layout_gravity="center"
    android:onClick="call"
    android:text="Call"
    android:textAllCaps="false"
    android:textSize="20dp" />

Thank you all.