Extending AdapterView | 易学教程

问题

i'm trying to make (for learning purposes) my own implementation of a simple AdapterView where items comes from an basic Adapter (ImageAdapter from sdk samples).

Actual code is like this:

    public class MyAdapterView extends AdapterView<ImageAdapter> implements AdapterView.OnItemClickListener{
    private ImageAdapter mAdapter;
    public MyAdapterView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initThings();
    }
    private void initThings(){
        setOnItemClickListener(this);
    }
    @Override
    public ImageAdapter getAdapter() {
        // TODO Auto-generated method stub
        return mAdapter;
    }
    @Override
    public void setAdapter(ImageAdapter adapter) {
        // TODO Auto-generated method stub
        mAdapter=adapter;
        requestLayout();
    }
    View obtainView(int position) {
        View child = mAdapter.getView(position, null, this);
        return child;
    }
    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
     super.onLayout(changed, l, t, r, b);
        for(int i=0;i<mAdapter.getCount();i++){
            View child = obtainView(i);
            child.layout(10, 70*i, 70, 70);
            addViewInLayout(child, i, null, true);
        }
        this.invalidate();
    }
    @Override
    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
        Log.d("MYEXAMPLES","Clicked an item!");
    }
}

This isn't a coding masterpiece, it just displays a pseudo-listview with pictures. I know i could've used ListView, GridView, Spinner, etc. but i'm relative new to android and i'm trying to figure out some things on it.

Well, the question here is: Why is my onItemClick not firing?

Using the same ImageAdapter with a GridView, everything works ok, but when i use with above class, i get nothing. Inside AdapterView.java there is code for those click, longclick, etc events... so why can't i just fire them? Maybe i'm misunderstanding basic things on how AdapterView works? Should I extend other base classes instead? And why?

Hoping to find more experienced guidance on here, thanks in advance.

回答1:

If you take a look into AdapterView's sources, you'll see that the OnItemClickListener gets invoked in a method, called performItemClick:

public boolean performItemClick(View view, int position, long id) {
    if (mOnItemClickListener != null) {
        // ...
        mOnItemClickListener.onItemClick(this, view, position, id);
        return true;
    }
    return false;
}

However, if you search the AdapterView source for where this method is used, you'll see that it isn't called anywhere!

Indeed, if you check the source of the Gallery for example, you'll see that the performItemClick is called within the handling of the onSingleTapUp or onKeyUp events.

If you want to use that, you have to detect when a user clicks somewhere and call performItemClick on your own.

回答2:

Instead of extending the AdapterView, why dont you try with the baseAdapter. When you costumize your Adapter, it has oen method given below.

getView(int position, View convertView,ViewGroup group)

in above method you can access the layout for each list item of the listview and here you can set the all supported events for each control.

回答3:

I am playing around with something similar and i am using onItem*Selected*Listener which may be more what you are looking for.

来源：https://stackoverflow.com/questions/2563897/extending-adapterview

标签

android

android-adapterview