I've created a custom component that looks and works similar to the iPhone's UIPicker. For a single wheel, I used an excellent solution available from this project: http://code.google.com/p/android-wheel/ (although I trimmed it down and added a couple of features). What I wanted to do is to create a single component that could be very easily placed in any layout, like so:
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"; android:id="@+id/layout" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <com.test.Meter android:layout_width="fill_parent" android:layout_height="wrap_content" android:gravity="center_vertical|center_horizontal" /> </LinearLayout> The component would then be given the number of dials to display in the code, and it would automatically adjust the size of the dials to the screen density. All of this was (mostly) done, and the custom component works fine on Android 2.2 and 2.3. However, on the earlier platforms the above layout produces an empty screen. My guess is that the earlier versions of the platform notice that com.test.Meter extends a LinearLayout (I will paste in the code for this component below) and that it has no children, so they just 'optimise it out', don't bother displaying it at all. I think so because one workaround that I've found is to add a dummy view inside of the Meter, then override the dispatchDraw on the component. Then the component is displayed, but probably the dummy view interferes with the layout because the first of the dials doesn't scroll properly. What I am looking for is a way to suppress any pre-2.2 layout optimisation and get my component displayed without funny workarounds. Any help will be highly appreciated. Here goes all the relevant code. First the Meter component itself (note that Dial is my modified version of the kankan.wheel.widget.WheelView from the project referenced above; I could potentially post its code but it is over 400 lines): package com.test; import java.util.ArrayList; import java.util.List; import android.content.Context; import android.graphics.Canvas; import android.util.AttributeSet; import android.view.ViewGroup; import android.widget.LinearLayout; public class Meter extends LinearLayout { // TODO: to be defined at runtime private final static int NUMBER_OF_DIALS = 6; private Context context; private List<Dial> dials; private int dialWidth; public Meter(Context ctx) { super(ctx); setWillNotDraw(false); context = ctx; } public Meter(Context ctx, AttributeSet attrs) { super(ctx, attrs); setWillNotDraw(false); context = ctx; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); int width = MeasureSpec.getSize(widthMeasureSpec); dialWidth = width / NUMBER_OF_DIALS; } protected void onLayout (boolean changed, int l, int t, int r, int b) { super.onLayout(changed, l, t, r, b); if (dials == null) { dials = new ArrayList<Dial>(); for (int i = 0; i < NUMBER_OF_DIALS; i++) { Dial d = new Dial(context); d.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams. WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT)); d.setRequiredWidth(dialWidth); d.setWillNotDraw(false); dials.add(d); this.addView(d); } } } protected boolean checkLayoutParams(ViewGroup.LayoutParams p) { return super.checkLayoutParams(p); } protected LinearLayout.LayoutParams generateLayoutParams (ViewGroup.LayoutParams p) { return super.generateLayoutParams(p); } } This is the trick that makes the component displayed on Android 1.6. First I change the layout to look like so: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"; android:id="@+id/layout" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <com.test.Meter android:layout_width="fill_parent" android:layout_height="wrap_content" android:gravity="center_vertical|center_horizontal" > <View android:layout_width="1px" android:layout_height="1px" /> </com.test.Meter> </LinearLayout> Then I add this method to the Meter: protected void dispatchDraw (Canvas canvas) { super.dispatchDraw(canvas); for (Dial d : dials) { d.draw(canvas); } } -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
