how to add views inside a custom View?

Question

I have a class like that, and there are about 10 of them

public class DataItemPlainView extends View{

    public DataItemPlainView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
    }}

Now I need to put TextView, ImageView etc inside this view. And when I call it from somewhere, I want to get my customView. setting a view to a custom layout is a case too.

Thanks

Answer 1

Your custom view needs to extend ViewGroup or one of the other classes that extends ViewGroup. For example, you could extend from RelativeLayout or LinearLayout if those layouts fits what your custom view needs to do.

Remember, even the layout classes are just another View. They just happen to have methods to add other views as children and have code to recursively measure and draw their children.

Answer 2

I would try extending some kind of Layout. Remember that (for the most part) they are also treated as Views. For more information/deciding which Layout to pick, try looking here:

http://developer.android.com/guide/topics/ui/layout-objects.html

Answer 3

Messing with the margins to achieve absolute positioning is WRONG. That won't scale up if you ever need the margins.

Steal the code from Android, modify it, and then use your "not deprecated" absolute layout.

AbsoluteLayout is deprecated because they don't want to support it, not because it doesn't work.

Screw that, their layouts don't do what we need, so what do they recommend? custom view.

So here it is (refactored, without style (puke) support):

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RemoteViews.RemoteView;


/**
 * A layout that lets you specify exact locations (x/y coordinates) of its
 * children. Absolute layouts are less flexible and harder to maintain than
 * other types of layouts without absolute positioning.
 *
 */
@RemoteView
public class DCAbsoluteLayout extends ViewGroup {
    int mPaddingLeft, mPaddingRight, mPaddingTop, mPaddingBottom;

    public DCAbsoluteLayout(Context context) {
        super(context);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int count = getChildCount();

        int maxHeight = 0;
        int maxWidth = 0;

        // Find out how big everyone wants to be
        measureChildren(widthMeasureSpec, heightMeasureSpec);

        // Find rightmost and bottom-most child
        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            if (child.getVisibility() != GONE) {
                int childRight;
                int childBottom;

                DCAbsoluteLayout.LayoutParams lp
                        = (DCAbsoluteLayout.LayoutParams) child.getLayoutParams();

                childRight = lp.x + child.getMeasuredWidth();
                childBottom = lp.y + child.getMeasuredHeight();

                maxWidth = Math.max(maxWidth, childRight);
                maxHeight = Math.max(maxHeight, childBottom);
            }
        }

        // Account for padding too
        maxWidth += mPaddingLeft + mPaddingRight;
        maxHeight += mPaddingTop + mPaddingBottom;

        // Check against minimum height and width
        maxHeight = Math.max(maxHeight, getSuggestedMinimumHeight());
        maxWidth = Math.max(maxWidth, getSuggestedMinimumWidth());

        setMeasuredDimension(resolveSizeAndState(maxWidth, widthMeasureSpec, 0),
                resolveSizeAndState(maxHeight, heightMeasureSpec, 0));
    }

    /**
     * Returns a set of layout parameters with a width of
     * {@link ViewGroup.LayoutParams#WRAP_CONTENT},
     * a height of {@link ViewGroup.LayoutParams#WRAP_CONTENT}
     * and with the coordinates (0, 0).
     */
    @Override
    protected ViewGroup.LayoutParams generateDefaultLayoutParams() {
        return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, 0, 0);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t,
            int r, int b) {
        int count = getChildCount();

        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            if (child.getVisibility() != GONE) {

                DCAbsoluteLayout.LayoutParams lp =
                        (DCAbsoluteLayout.LayoutParams) child.getLayoutParams();

                int childLeft = mPaddingLeft + lp.x;
                int childTop = mPaddingTop + lp.y;
                child.layout(childLeft, childTop,
                        childLeft + child.getMeasuredWidth(),
                        childTop + child.getMeasuredHeight());

            }
        }
    }

    // Override to allow type-checking of LayoutParams.
    @Override
    protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
        return p instanceof DCAbsoluteLayout.LayoutParams;
    }

    @Override
    protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
        return new LayoutParams(p);
    }

    @Override
    public boolean shouldDelayChildPressedState() {
        return false;
    }

    public static class LayoutParams extends ViewGroup.LayoutParams {
        /**
         * The horizontal, or X, location of the child within the view group.
         */
        public int x;
        /**
         * The vertical, or Y, location of the child within the view group.
         */
        public int y;

        /**
         * Creates a new set of layout parameters with the specified width,
         * height and location.
         *
         * @param width the width, either {@link #MATCH_PARENT},
                  {@link #WRAP_CONTENT} or a fixed size in pixels
         * @param height the height, either {@link #MATCH_PARENT},
                  {@link #WRAP_CONTENT} or a fixed size in pixels
         * @param x the X location of the child
         * @param y the Y location of the child
         */
        public LayoutParams(int width, int height, int x, int y) {
            super(width, height);
            this.x = x;
            this.y = y;
        }

        /**
         * {@inheritDoc}
         */
        public LayoutParams(ViewGroup.LayoutParams source) {
            super(source);
        }

    }
}

In general, Android UI is a nightmare. Consider using a webview for your entire project. As far as working with the system goes, "it's okay", but that UI is a train-wreck.

HTML has always been the way to go for styles and dynamic UI content. Nothing else rivals it, but custom drawn UI (in terms of performance).