How to Enable LongCLicks on my ListView?

问题:

I'm trying to enable Long Clicks in my app and I can't get it to compile. I looked at the examples from previous questions here, but I can't get any of them to compile. My main activity is declared as:

import android.widget.AdapterView.OnItemLongClickListener;
public class LinearLayoutDemo extends ListActivity implements OnClickListener, OnItemClickListener, OnItemLongClickListener {

In the onCreate() method, I put this:

getListView().setOnItemLongClickListener(this);

And for my ListView (myLV), I did this:

myLV1.setOnItemLongClickListener(new View.OnItemClickListener() {
    @Override public boolean onLongClick(View v) {
        Log.d(TAG, "setOnItemLongClickListener() called for myLV");
        return(true);
    }
});

I think the above must be wrong, but I don't know why. The compiler error is

LinearLayoutDemo.java:45: com.commonsware.android.linearpct.LinearLayoutDemo is not abstract and does not override abstract method onItemLongClick(android.widget.AdapterView<?>,android.view.View,int,long) in android.widget.AdapterView.OnItemLongClickListener
[javac] public class LinearLayoutDemo extends ListActivity implements OnClickListener, OnItemClickListener, OnItemLongClickListener {

LinearLayoutDemo.java:287: cannot find symbol
[javac] symbol  : class OnItemLongClickListener
[javac] location: class android.view.View
[javac]         myLV1.setOnItemLongClickListener(new View.OnItemLongClickListener() {
[javac]                                                  ^

*************** UPDATE ***************

I got rid of OnItemLongClickListener in the ListActivity class definition. I also got rid of this

getListView().setOnItemLongClickListener(this);

Then I added this code and it worked ( I don't know why):

myLV1.setOnItemLongClickListener(new OnItemLongClickListener() {
    public boolean onItemLongClick(AdapterView<?> parent, View v, int position, long id) {
        Log.d(TAG, "onItemLongClick() for LV1");
        return true;
    }
});

It seems pretty simple, so I'm sticking with it, unless someone can tell me I shouldn't do it like this.

************ EDIT **************

Okay, I have the Long Clicks working. How can I tell which item I long-clicked? I had assumed that myLV1.getCheckedItemPosition() would work, but it doesn't.

Nevermind, it's in 'position' parameter to onItemLongClick().

回答1:

What you are doing here is practicly setting the onLongClickListener twice:

1. getListView().setOnItemLongClickListener(this);

here you set the Activity to be the Listener as it implements the onLongClickListener interface.

2. myLV1.setOnItemLongClickListener(new View.OnItemClickListener() {....

Here you are creating a new onItemClickListener and trying to apply it again to the list. remove this part from your activity code.

and add unimplemented method:

onLongClick that should be in your Activity as soon as you activity trying to implement onLongClickListener

In this method you can specify what are the actions in case of a long click.

UPDATE:

1. Right click on the error.
2. Add unimplemented methods.

This will add you this code to the class:

@Override
public boolean onItemLongClick(AdapterView<?> arg0, View arg1, int arg2,
        long arg3) {
    // TODO Auto-generated method stub
    return false;
}

in it define your action for Long click.

回答2:

You can do basically two things:

1. Remove the line getListView().setOnItemLongClickListener(this); since you didn't implemented/overrided the onItemLongClick method of AdapterView.OnItemLongClickListener

2. In myLV1.setOnItemLongClickListener you must create a instance of AdapterView.OnItemLongClickListener and not the View.OnItemLongClickListener

回答3:

Do you want to create a context-menu on long-clicking a ListView-Item?

If so the easiest way to achieve this is by using registerForContextMenu(findViewById(android.R.id.list)); inside your onCreate-method.

Then you have to override the methods onCreateContextMenu and onContextItemSelected like so:

onCreateContextMenu

@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu, v, menuInfo);
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.my_context_layout, menu);
}

onContextItemSelected

@Override
public boolean onContextItemSelected(MenuItem item) {
    AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();

    switch (item.getItemId()) {
        case R.id.my_item1:
            doSomething();
            return true;
        case R.id.my_item2:
            doSomething();
            return true;
        default:
            return super.onContextItemSelected(item);
    }
}