I have a MainActivity
that shows a listview
with items that I add dynamically to it. So far everything works. Now wanted to create a button
that should delete the listview item
that was clicked on. Here is the code I came with.
MainActivity
package news;
import android.app.Activity;
import android.content.Intent;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
ArrayAdapter<String> newslist_adapter;
ArrayList<String> new_subject = new ArrayList<>();
ArrayList<String> new_post = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ListView post_view = findViewById(R.id.news_feed);
FloatingActionButton add_post_button = findViewById(R.id.post_btn);
//create click event and pass values of arrays
post_view.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
Intent intent = new Intent(getApplicationContext(), full_post_activity.class);
intent.putExtra("Subject", new_subject);
intent.putExtra("Post", new_post);
intent.putExtra("position", id);
// getApplicationContext().startActivity(intent);
startActivityForResult(intent, 2);
}
});
//create button connection and create keylistener
add_post_button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, addpost_activity.class);
startActivityForResult(intent, 1);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
final ListView post_view = findViewById(R.id.news_feed);
if (requestCode == 1) {
if(resultCode == Activity.RESULT_OK){
//get subject and post from second activity
String new_subject_value = data.getStringExtra("newSubject");
String new_post_value = data.getStringExtra("newPost");
new_subject.add(new_subject_value);
new_post.add(new_post_value);
newslist_adapter = new ArrayAdapter<>(
MainActivity.this,
android.R.layout.simple_expandable_list_item_1, new_subject);
post_view.setAdapter(newslist_adapter);
}
}
if (requestCode == 2) {
if(resultCode == Activity.RESULT_OK){
String item2delete = data.getStringExtra("id");
new_subject.remove(item2delete);
newslist_adapter = new ArrayAdapter<>(
MainActivity.this,
android.R.layout.simple_expandable_list_item_1, new_subject);
post_view.setAdapter(newslist_adapter);
}
}
}
}
SecondActivity
package news;
import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import java.util.ArrayList;
public class full_post_activity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.full_post_activity);
final int id = getIntent().getExtras().getInt("id");
//create view reference
final TextView subject_edit = findViewById(R.id.subject_input);
final TextView post_edit = findViewById(R.id.post_input);
//create button reference
Button delete_button = findViewById(R.id.full_post_delete_btn);
//create click event
delete_button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(getApplicationContext(), MainActivity.class);
intent.putExtra("id", id);
setResult(Activity.RESULT_OK, intent);
finish();
}
});
ArrayList<String> subject_array = (ArrayList<String>) getIntent().getSerializableExtra("Subject");
ArrayList<String> post_array = (ArrayList<String>) getIntent().getSerializableExtra("Post");
String subject_string = subject_array.get(0);
String post_string = post_array.get(0);
//set textview text
subject_edit.setText(subject_string);
post_edit.setText(post_string);
}
}
My problem now is that the delete button
doesn't do anything besides returning to the MainActivity
. What am I doing wrong?
You cannot get id value to MainActivity. This line in second activity cause problem
final int id = getIntent().getExtras().getInt("id");
In Main Activity, You can put id value using name index "position"
intent.putExtra("position", id);
So you should change them to
In Second Activity
final int id = getIntent().getExtras().getInt("position");
or Main Activity
intent.putExtra("id", id);
UPDATED try this in Main Activity
intent.putExtra("id", position);
If you want to stay in the activity where the delete button is I would suggest creating a getter and a setter for the list behind your ListView(Easily generate them with ALT+INSERT).
You can then make an instance of your MainActivity inside the delete_buttons OnClick methode and get said List with the getter. Remove the Item you need to remove and update the list with your setter, again using your MainActivity instance.
Edit: here are some code samples
Getter and Setter:
public ArrayList<String> getNewPost() {
return this.new_post;
}
public void setNewPost(ArrayList<String> np) {
this.new_post = np;
}
delete_button OnClick methode:
delete_button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
MainActivity main=new MainActivity();
ListView<String> np=main.getNewPost();
np.remove("StringToRemove");
main.setNewPost(np);
}
});
I would also suggest you to make a back_button to check if the list was updated, you can use your old delete_button onclick for that.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.