Question

I’m trying to make a ListView with clickable list entries. What I want it to do, when an entry is clicked, is display a toast message. However, as soon as I click an entry, the application crashes. I don’t really see why it does this. This is my code:

package com.andriesse.android.dailyproductivity;

import java.util.ArrayList;

import com.andriesse.android.dailyproductivity.MyDB;

public class Main extends Activity implements OnItemClickListener, OnKeyListener {

ListView listview;

MyDB mydb;
TaskAdapter myadapter;

private class MyTask {
    public MyTask(String t) {
        task = t;
    }

    public String task;
}

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.main);

    listview = (ListView) findViewById(R.id.listview);
    listview.setOnItemClickListener(this);

    mydb = new MyDB(this);
    mydb.open();

    myadapter = new TaskAdapter(this);

    listview.setAdapter(myadapter); 

}

public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    String item = ((TextView)view).getText().toString();
    Toast.makeText(getBaseContext(), item, Toast.LENGTH_LONG).show();
}

private class TaskAdapter extends BaseAdapter {
    private LayoutInflater layoutinflater;
    private ArrayList<MyTask> arraylist;

    public TaskAdapter(Context context) {
        layoutinflater = LayoutInflater.from(context);
        arraylist = new ArrayList<MyTask>();
        getdata();
    }

    public void getdata() {
        Cursor c = mydb.getTasks();
        startManagingCursor(c);
        if (c.moveToFirst()) {
            do {
                String task = c.getString(c
                        .getColumnIndex(Constants.TASK_NAME));
                MyTask temp = new MyTask(task);
                arraylist.add(temp);
            } while (c.moveToNext());
        }
    }

    public int getCount() {
        return arraylist.size();
    }

    public MyTask getItem(int i) {
        return arraylist.get(i);
    }

    public long getItemId(int i) {
        return i;
    }

    public View getView(int i, View view, ViewGroup group) {            
        ViewHolder holder;
        if (view == null || view.getTag() == null) {
            view = layoutinflater.inflate(R.layout.rowlayout, null);
            holder = new ViewHolder();
            holder.textview = (TextView) view.findViewById(R.id.textview);
            view.setTag(holder);
        } else {
            holder = (ViewHolder) view.getTag();
        }

        holder.mytask = getItem(i);
        holder.textview.setText(holder.mytask.task);

        return view;
    }

    public class ViewHolder {
        MyTask mytask;
        TextView textview;
    }
}

private void addItem(String item) {
    if (item.length() > 0) {
        try {
            saveTaskToDB(item);
            myadapter.arraylist.add(new MyTask(item));
            myadapter.notifyDataSetChanged();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public void saveTaskToDB(String task) {
    mydb.insertTask(task);
}

@Override
public void onDestroy() {
    super.onDestroy();
    mydb.close();
}

public boolean onKey(View v, int keyCode, KeyEvent event) {
    // TODO Auto-generated method stub
    return false;
}

}

And here’s my LogCat log:

06-09 20:50:41.743: E/AndroidRuntime(194): Uncaught handler: thread main exiting due to uncaught exception
06-09 20:50:41.773: E/AndroidRuntime(194): java.lang.ClassCastException: android.widget.RelativeLayout
06-09 20:50:41.773: E/AndroidRuntime(194):  at com.andriesse.android.dailyproductivity.Main.onItemClick(Main.java:57)
06-09 20:50:41.773: E/AndroidRuntime(194):  at android.widget.AdapterView.performItemClick(AdapterView.java:284)
06-09 20:50:41.773: E/AndroidRuntime(194):  at android.widget.ListView.performItemClick(ListView.java:3285
06-09 20:50:41.773: E/AndroidRuntime(194):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:1640)
06-09 20:50:41.773: E/AndroidRuntime(194):  at android.os.Handler.handleCallback(Handler.java:587)
06-09 20:50:41.773: E/AndroidRuntime(194):  at android.os.Handler.dispatchMessage(Handler.java:92)
06-09 20:50:41.773: E/AndroidRuntime(194):  at android.os.Looper.loop(Looper.java:123)
06-09 20:50:41.773: E/AndroidRuntime(194):  at android.app.ActivityThread.main(ActivityThread.java:4363)
06-09 20:50:41.773: E/AndroidRuntime(194):  at java.lang.reflect.Method.invokeNative(Native Method)
06-09 20:50:41.773: E/AndroidRuntime(194):  at java.lang.reflect.Method.invoke(Method.java:521)
06-09 20:50:41.773: E/AndroidRuntime(194):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
06-09 20:50:41.773: E/AndroidRuntime(194):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
06-09 20:50:41.773: E/AndroidRuntime(194):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

post the stack trace. We are more likely to be able to help if you add it.

I can tell you though the problem is probably from how you are trying to cast the view to TextView. The view that is coming in as the parameter is probably not the TextView, it is likely some kind of parent Layout. You probably need to use

TextView mTxt = (TextView)view.findViewById(R.id.yourEdtTxtID); 

to get a reference to the TextView

Also though you probably shouldn’t be changing the text on a Row’s TextView manually in the click listener like that. If you need to change the value you should be using an Adapter with a data structure that will allow you to change the value to whatever you like, and once the Adapter is set on your ListView it will update the Views on the screen automatically for you when you change the data in your structure.