adding onClick listener to gridView items (to laun

问题:

I have a gridView and I'd like to launch a different intent depending on the position of the item clicked.

I've instantiated the following onClick listener which includes the value for position:

gridview.setOnItemClickListener(new OnItemClickListener() {
    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
        Toast.makeText(HelloGridView.this, "" + position, Toast.LENGTH_SHORT).show();
    }
});

But I believe I'll need to add an if statement within it to determine which intent to launch depending on this position. So far I've come up with the following but I do not believe it is exactly what I'm looking for.

if position = 1 { Intent intent = new Intent(this, Activity1.class); }else if position = 2 { Intent intent = new Intent(this, Activity1.class); }

Any suggestions are greatly appreciated.

/** * This activity presents a screen with a grid on which images can be added and * moved around. It also defines areas on the screen where the dragged views can * be dropped. Feedback is provided to the user as the objects are dragged over * these drop zones. * *

* Like the DragActivity in the previous version of the DragView example * application, the code here is derived from the Android Launcher code. * *

* The original Launcher code required a long click (press) to initiate a * drag-drop sequence. If you want to see that behavior, set the variable * mLongClickStartsDrag to true. It is set to false below, which means that any * touch event starts a drag-drop. * */

public class DragActivity extends Activity implements View.OnLongClickListener,
View.OnClickListener, View.OnTouchListener // ,
// AdapterView.OnItemClickListener
{

    /**
     */
    // Constants

    private static final int HIDE_TRASHCAN_MENU_ID = Menu.FIRST;
    private static final int SHOW_TRASHCAN_MENU_ID = Menu.FIRST + 1;
    private static final int ADD_OBJECT_MENU_ID = Menu.FIRST + 2;
    private static final int CHANGE_TOUCH_MODE_MENU_ID = Menu.FIRST + 3;
    private boolean isErase = true;
    private EditText et;
    private TextView tx;

    /**
     */
    // Variables

    private DragController mDragController; // Object that handles a drag-drop
    // sequence. It intersacts with
    // DragSource and DropTarget
    // objects.
    private DragLayer mDragLayer; // The ViewGroup within which an object can be
    // dragged.
    private DeleteZone mDeleteZone; // A drop target that is used to remove
    // objects from the screen.
    private int mImageCount = 0; // The number of images that have been added to
    // screen.
    private ImageCell mLastNewCell = null; // The last ImageCell added to the
    // screen when Add Image is clicked.
    private boolean mLongClickStartsDrag = true; // If true, it takes a long
    // click to start the drag
    // operation.
    // Otherwise, any touch
    // event starts a drag.

    public static final boolean Debugging = false; // Use this to see extra
    // toast messages.

    /**
     */
    // Methods

    /**
     * Add a new image so the user can move it around. It shows up in the
     * image_source_frame part of the screen.
     * 
     * @param resourceId
     *            int - the resource id of the image to be added
     */

    public void addNewImageToScreen(int resourceId) {
        if (mLastNewCell != null)
            mLastNewCell.setVisibility(View.GONE);

        FrameLayout imageHolder = (FrameLayout) findViewById(R.id.image_source_frame);
        if (imageHolder != null) {
            FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(
                    LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT,
                    Gravity.CENTER);
            ImageCell newView = new ImageCell(this);
            newView.setImageResource(resourceId);
            imageHolder.addView(newView, lp);
            newView.mEmpty = false;
            newView.mCellNumber = -1;
            mLastNewCell = newView;
            mImageCount++;

            // Have this activity listen to touch and click events for the view.
            newView.setOnClickListener(this);
            newView.setOnLongClickListener(this);
            newView.setOnTouchListener(this);

        }
    }

    /**
     * Add one of the images to the screen so the user has a new image to move
     * around. See addImageToScreen.
     * 
     */

    public void addNewImageToScreen() {
        int resourceId = R.drawable.sqwhite;
        addNewTextToScreen();
        int m = mImageCount % 3;

        if (m == 1)
            resourceId = R.drawable.sqdrk;

        else if (m == 2)
            resourceId = R.drawable.sqwhite;
        addNewImageToScreen(resourceId);

    }

    private void addNewTextToScreen() {
        // TODO Auto-generated method stub

    //  et.setVisibility(View.VISIBLE);
        if (isErase) {
            tx.setText(et.getText().toString());
        } else {
            tx.setText("");
            et.setVisibility(View.GONE);
        }
        isErase = !isErase;
    }

    /**
     * Handle a click on a view.
     * 
     */

    public void onClick(View v) {
        if (mLongClickStartsDrag) {
            // Tell the user that it takes a long click to start dragging.
            //toast("Press and hold to drag an image.");


        }
    }

    /**
     * Handle a click of the Add Image button
     * 
     */

    public void onClickAddImage(View v) {
        addNewImageToScreen();
    }

    /**
     * onCreate - called when the activity is first created.
     * 
     * Creates a drag controller and sets up three views so click and long click
     * on the views are sent to this activity. The onLongClick method starts a
     * drag sequence.
     * 
     */

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.demo);
        et = (EditText) findViewById(R.id.editText1);
        et.setVisibility(View.INVISIBLE);
        tx = (TextView) findViewById(R.id.textView1);

        GridView gridView = (GridView) findViewById(R.id.image_grid_view);

        if (gridView == null)
            toast("Unable to find GridView");
        else {
            gridView.setAdapter(new ImageCellAdapter(this));
            // gridView.setOnItemClickListener (this);
        }

        mDragController = new DragController(this);
        mDragLayer = (DragLayer) findViewById(R.id.drag_layer);
        mDragLayer.setDragController(mDragController);
        mDragLayer.setGridView(gridView);

        mDragController.setDragListener(mDragLayer);
        // mDragController.addDropTarget (mDragLayer);

        mDeleteZone = (DeleteZone) findViewById(R.id.delete_zone_view);

        // Give the user a little guidance.
        Toast.makeText(getApplicationContext(),
                getResources().getString(R.string.instructions),
                Toast.LENGTH_LONG).show();
    }

    /**
     * Build a menu for the activity.
     * 
     */

    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);

        menu.add(0, HIDE_TRASHCAN_MENU_ID, 0, "Hide Trashcan").setShortcut('1',
                'c');
        menu.add(0, SHOW_TRASHCAN_MENU_ID, 0, "Show Trashcan").setShortcut('2',
                'c');
        menu.add(0, ADD_OBJECT_MENU_ID, 0, "Add View").setShortcut('9', 'z');
        menu.add(0, CHANGE_TOUCH_MODE_MENU_ID, 0, "Change Touch Mode");

        return true;
    }

    /**
     * Handle a click of an item in the grid of cells.
     * 
     */

    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
        ImageCell i = (ImageCell) v;
        trace("onItemClick in view: " + i.mCellNumber);
    }

    /**
     * Handle a long click. If mLongClick only is true, this will be the only
     * way to start a drag operation.
     * 
     * @param v
     *            View
     * @return boolean - true indicates that the event was handled
     */

    public boolean onLongClick(View v) {
        if (mLongClickStartsDrag) {

            // trace ("onLongClick in view: " + v + " touchMode: " +
            // v.isInTouchMode ());

            // Make sure the drag was started by a long press as opposed to a
            // long click.
            // (Note: I got this from the Workspace object in the Android
            // Launcher code.
            // I think it is here to ensure that the device is still in touch
            // mode as we start the drag operation.)
            if (!v.isInTouchMode()) {
                toast("isInTouchMode returned false. Try touching the view again.");
                return false;
            }
            return startDrag(v);
        }

        // If we get here, return false to indicate that we have not taken care
        // of the event.
        return false;
    }

    /**
     * Perform an action in response to a menu item being clicked.
     * 
     */

    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case HIDE_TRASHCAN_MENU_ID:
            if (mDeleteZone != null)
                mDeleteZone.setVisibility(View.INVISIBLE);
            return true;
        case SHOW_TRASHCAN_MENU_ID:
            if (mDeleteZone != null)
                mDeleteZone.setVisibility(View.VISIBLE);
            return true;
        case ADD_OBJECT_MENU_ID:
            // Add a new object to the screen;
            addNewImageToScreen();
            return true;
        case CHANGE_TOUCH_MODE_MENU_ID:
            mLongClickStartsDrag = !mLongClickStartsDrag;
            String message = mLongClickStartsDrag ? "Changed touch mode. Drag now starts on long touch (click)."
                    : "Changed touch mode. Drag now starts on touch (click).";
            Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG)
            .show();
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /**
     * This is the starting point for a drag operation if mLongClickStartsDrag
     * is false. It looks for the down event that gets generated when a user
     * touches the screen. Only that initiates the drag-drop sequence.
     * 
     */

    public boolean onTouch(View v, MotionEvent ev) {
        // If we are configured to start only on a long click, we are not going
        // to handle any events here.
        if (mLongClickStartsDrag)
            return false;

        boolean handledHere = false;

        final int action = ev.getAction();

        // In the situation where a long click is not needed to initiate a drag,
        // simply start on the down event.
        if (action == MotionEvent.ACTION_DOWN) {
            handledHere = startDrag(v);
        }

        return handledHere;
    }

    /**
     * Start dragging a view.
     * 
     */

    public boolean startDrag(View v) {
        DragSource dragSource = (DragSource) v;

        // We are starting a drag. Let the DragController handle it.
        mDragController.startDrag(v, dragSource, dragSource,
                DragController.DRAG_ACTION_MOVE);

        return true;
    }

    /**
     * Show a string on the screen via Toast.
     * 
     * @param msg
     *            String
     * @return void
     */

    public void toast(String msg) {
        Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_SHORT).show();
    } // end toast

    /**
     * Send a message to the debug log. Also display it using Toast if Debugging
     * is true.
     */

    public void trace(String msg) {
        Log.d("DragActivity", msg);
        if (!Debugging)
            return;
        toast(msg);
    }

} // end class

回答1:

from the android documentation for GridView:

gridview.setOnItemClickListener(new OnItemClickListener() {
    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
        Toast.makeText(HelloGridView.this, "" + position, Toast.LENGTH_SHORT).show();
    }
});

edit: It looks like the addNewImageToScreen() is where you are adding the ImageCells, so assuming that you can generate the intent in that scope..

Intent intent = new Intent(this, Activity1.class); // or whatever you want to run
ImageCell newView = ...
newView.setTag( intent );

then in your onItemClick: public void onItemClick(AdapterView parent, View v, int position, long id) { Toast.makeText(HelloGridView.this, "" + position, Toast.LENGTH_SHORT).show(); Intent intent = (Intent) v.getTag(); // now you can startActivity with your intent.. }

回答2:

Make a string array with your classes, the in the onItemClick () create another string declared with the position (item) clicked.

public class MainActivity extends Activity {

    String [] classes = {"act1",  "act2"}; // activity files

    GridView gridView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    gridView = (GridView) findViewById(R.id.gridView);
    gridView.setAdapter(new ImageAdapter(this));
    gridView.setOnItemClickListener(new OnItemClickListener() {
            @SuppressWarnings("rawtypes")
            public void onItemClick(AdapterView<?> parent, View v, int position, long id) {

            String pos = classes[position];

            try {
            Class start = Class.forName("com.company.app." + pos); //Your package name

            Intent i = new Intent(MainActivity.this, start);
            startActivity(i);
            } catch(ClassNotFoundException e){
            e.printStackTrace();
            }

            Toast.makeText(
                getApplicationContext(),
                ((TextView) v.findViewById(R.id.label))
                .getText(), Toast.LENGTH_SHORT).show();
            }
        });
    }
}