MainActivity.java

package com.example.hoa.dialog;

import android.app.DialogFragment;
import android.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    static TextView hello;


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

        //TextView

        hello = (TextView) findViewById(R.id.hiii);

        //Button
        ImageButton add_warning = findViewById(R.id.addwarning);
        add_warning.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FragmentManager newFragment = getFragmentManager();
                DialogFragm myDialog = new DialogFragm();
                Dialog2 dialog2 = (Dialog2) getFragmentManager().findFragmentByTag("Dialog2");
                myDialog.setTargetFragment(dialog2,1);
                myDialog.show(newFragment,null);
            }
        });

    }

}