[英]Delete a listview item from activity on button click from another activity
我有一個MainActivity
,它顯示一個listview
其中包含我動態添加到其中的項目。 到目前為止,一切正常。 現在想創建一個button
,該button
應該刪除被單擊的listview item
。 這是我附帶的代碼。
主要活動
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);
}
}
我現在的問題是, delete button
除了返回MainActivity
之外什么也不做。 我究竟做錯了什么?
您無法將ID值獲取給MainActivity。 第二行中的此行導致問題
final int id = getIntent().getExtras().getInt("id");
在主要活動中,您可以使用名稱索引“ position”放置id值
intent.putExtra("position", id);
所以你應該將它們更改為
在第二活動中
final int id = getIntent().getExtras().getInt("position");
或主要活動
intent.putExtra("id", id);
更新在主要活動中嘗試此
intent.putExtra("id", position);
如果您想停留在刪除按鈕所在的活動中,建議您為ListView后面的列表創建一個吸氣劑和一個吸氣劑(用ALT + INSERT輕松生成)。
然后,您可以在delete_buttons OnClick方法內創建MainActivity的實例,並使用getter獲取所說的List。 再次使用MainActivity實例,刪除您需要刪除的Item並使用setter更新列表。
編輯:這是一些代碼示例
Getter和Setter:
public ArrayList<String> getNewPost() {
return this.new_post;
}
public void setNewPost(ArrayList<String> np) {
this.new_post = np;
}
delete_button OnClick方法:
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);
}
});
我還建議您創建一個back_button來檢查列表是否已更新,您可以為此使用舊的delete_button onclick。
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