在另一个活动的列表视图中添加项目

Question

我是Android开发的新手，我发现编程很难，这就是为什么我要求你的帮助。我正在研究项目，我可以在列表上添加注释。我还有一个活动，我编辑笔记，我想在那里添加一个按钮，当我点击它，在noteActivity中添加一个项目在我的笔记前面。我想在笔记的前面加上一个标记为重要标记的解释标记。我真的不知道怎么做，我在哭。请有人帮我吗？有什么例子我怎么能这样做？

以下是笔记的主要活动：

公共类MainActivity扩展了ListActivity {

private static final int EDITOR_ACTIVITY_REQUEST = 1001;
private NotesDataSource datasource;
List<NoteItem> notesList;

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

    datasource = new NotesDataSource(this);

    refreshDisplay();

}

private void refreshDisplay() {
    notesList= datasource.findAll();
    ArrayAdapter<NoteItem> adapter =
            new ArrayAdapter<>(this, R.layout.list_item_layout, notesList);
    setListAdapter(adapter);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    if (item.getItemId() == R.id.action_create) {
     createNote();  
    }

    return super.onOptionsItemSelected(item);
}

private void createNote() {

    NoteItem note = NoteItem.getNew();
 Intent intent = new Intent(this, NoteEditorActivity.class);
 intent.putExtra("key", note.getKey());
 intent.putExtra("text", note.getText());
 startActivityForResult(intent, EDITOR_ACTIVITY_REQUEST);
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    NoteItem note = notesList.get(position);
     Intent intent = new Intent(this, NoteEditorActivity.class);
     intent.putExtra("key", note.getKey());
     intent.putExtra("text", note.getText());
     startActivityForResult(intent, EDITOR_ACTIVITY_REQUEST);

}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == EDITOR_ACTIVITY_REQUEST && resultCode == RESULT_OK ) {
        NoteItem note = new NoteItem();
        note.setKey(data.getStringExtra("key"));
        note.setText(data.getStringExtra("text"));
        datasource.update(note);
        refreshDisplay();
    }
}
 }

这是我的NoteEditorActivity

    public class NoteEditorActivity extends Activity{

private NoteItem note;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_note_editor);
    getActionBar().setDisplayHomeAsUpEnabled(true);

Intent intent = this.getIntent(); 
note = new NoteItem();
note.setKey(intent.getStringExtra("key"));
note.setText(intent.getStringExtra("text"));

EditText et = (EditText)findViewById(R.id.headerText);
et.setText(note.getText());
et.setSelection(note.getText().length());
}

private void saveAndFinish(){
    EditText et = (EditText)findViewById(R.id.headerText);
    String headerText = et.getText().toString();

    Intent intent = new Intent();
     intent.putExtra("key", note.getKey());
     intent.putExtra("text", headerText);
     setResult(RESULT_OK, intent);
     finish();
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId()== android.R.id.home) {
        saveAndFinish();
    }
    return false;
}

@Override
public void onBackPressed() {
    saveAndFinish();
}

     }

Answer 1

阅读ArrayAdapter部分。

对于解决方案，您必须将标记的信息添加到NoteItem类中，并检查适配器中的getter（将它们添加到您的类中）

您需要编写自己的自定义适配器。

public class MainActivity extends ListActivity {

private static final int EDITOR_ACTIVITY_REQUEST = 1001;
private NotesDataSource datasource;
List<NoteItem> notesList;

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

    datasource = new NotesDataSource(this);

    refreshDisplay();

}

private void refreshDisplay() {
    notesList= datasource.findAll();
    ArrayAdapter<NoteItem> adapter =
            new CustomAdapter(this, R.layout.custom_layout, notesList);
    setListAdapter(adapter);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    if (item.getItemId() == R.id.action_create) {
     createNote();  
    }

    return super.onOptionsItemSelected(item);
}

private void createNote() {

    NoteItem note = NoteItem.getNew();
 Intent intent = new Intent(this, NoteEditorActivity.class);
 intent.putExtra("key", note.getKey());
 intent.putExtra("text", note.getText());
 startActivityForResult(intent, EDITOR_ACTIVITY_REQUEST);
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    NoteItem note = notesList.get(position);
     Intent intent = new Intent(this, NoteEditorActivity.class);
     intent.putExtra("key", note.getKey());
     intent.putExtra("text", note.getText());
     startActivityForResult(intent, EDITOR_ACTIVITY_REQUEST);

}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == EDITOR_ACTIVITY_REQUEST && resultCode == RESULT_OK ) {
        NoteItem note = new NoteItem();
        note.setKey(data.getStringExtra("key"));
        note.setText(data.getStringExtra("text"));
        datasource.update(note);
        refreshDisplay();
    }
}

private class CustomAdapter extend ArrayAdapter<NoteItem> {

    private int mResourceId;
    private List<NoteItem> mData;

    public CustomAdapter(Context context, int resourceId, List<NoteItem> data) {
       super(context, resourceId, data);
       mResourceId = resourceId;
       mData = data;
    }

     @Override
     public View getView(int position, View convertView, ViewGroup parent) {
        NoteItem item = mData.get(position);        

        if (convertView == null) {
            convertView = LayoutInflater.from(mContext).inflate(resourceId, null);  
        }

        TextView titleTV = (TextView) convertView.findViewById(R.id.title);
        TextView textTV = (TextView) convertView.findViewById(R.id.text);
        CheckBox markedCB = (CheckBox) convertView.findViewById(R.id.mark);

        titleTV.setText(item.getKey());
        textTV.setText(item.getText());
        markedCB.setChecked(itemt.getMarked());

        return convertView;         
     }
}
 }

将以下内容另存为custom_layout

<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">


     <CheckBox
       android:id="@+id/mark"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content" />

    <TextView
       android:id="@+id/title"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content" />

        <TextView
       android:id="@+id/text"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content" />

</LinearLayout>

你总是创建一个新的适配器，这不是一个好方法。请改用clear（）和add（）： Docu