Android UI How to - Create custom layout

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The following code shows how to create custom layout.

Example

res/layout/main.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright (c) 2012 Manning
  See the file license.txt for copying permission.
-->
<FrameLayout xmlns:cascade="http://schemas.android.com/apk/res/com.manning.androidhacks.hack003"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <com.manning.androidhacks.hack003.view.CascadeLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        cascade:horizontal_spacing="30dp"
        cascade:vertical_spacing="20dp" >

        <View
            android:layout_width="100dp"
            android:layout_height="150dp"
            cascade:layout_vertical_spacing="90dp"
            android:background="#FF0000" />

        <View
            android:layout_width="100dp"
            android:layout_height="150dp"
            android:background="#00FF00" />

        <View
            android:layout_width="100dp"
            android:layout_height="150dp"
            android:background="#0000FF" />
    </com.manning.androidhacks.hack003.view.CascadeLayout>
</FrameLayout>

res/layout/framelayout_with_margins.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright (c) 2012 Manning
  See the file license.txt for copying permission.
-->

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <View
        android:layout_width="100dp"
        android:layout_height="150dp"
        android:background="#FF0000" />

    <View
        android:layout_width="100dp"
        android:layout_height="150dp"
        android:layout_marginLeft="30dp"
        android:layout_marginTop="20dp"
        android:background="#00FF00" />

    <View
        android:layout_width="100dp"
        android:layout_height="150dp"
        android:layout_marginLeft="60dp"
        android:layout_marginTop="40dp"
        android:background="#0000FF" />

</RelativeLayout>

Main Activity java

/*******************************************************************************
 * Copyright (c) 2012 Manning// w  w w .  j ava 2  s .c  o m
 * See the file license.txt for copying permission.
 ******************************************************************************/
package com.manning.androidhacks.hack003;

import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {

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

Custom layout Java file

/*******************************************************************************
 * Copyright (c) 2012 Manning/*  w w  w  . j ava 2s  .c  o m*/
 * See the file license.txt for copying permission.
 ******************************************************************************/

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

import com.manning.androidhacks.hack003.R;

public class CascadeLayout extends ViewGroup {

  private int mHorizontalSpacing;
  private int mVerticalSpacing;

  public CascadeLayout(Context context, AttributeSet attrs) {
    super(context, attrs);

    TypedArray a = context.obtainStyledAttributes(attrs,
        R.styleable.CascadeLayout);

    try {
      mHorizontalSpacing = a.getDimensionPixelSize(
          R.styleable.CascadeLayout_horizontal_spacing,
          getResources().getDimensionPixelSize(
              R.dimen.cascade_horizontal_spacing));

      mVerticalSpacing = a.getDimensionPixelSize(
          R.styleable.CascadeLayout_vertical_spacing, getResources()
              .getDimensionPixelSize(R.dimen.cascade_vertical_spacing));
    } finally {
      a.recycle();
    }

  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int width = getPaddingLeft();
    int height = getPaddingTop();
    int verticalSpacing;

    final int count = getChildCount();
    for (int i = 0; i < count; i++) {
      verticalSpacing = mVerticalSpacing;

      View child = getChildAt(i);
      measureChild(child, widthMeasureSpec, heightMeasureSpec);

      LayoutParams lp = (LayoutParams) child.getLayoutParams();
      width = getPaddingLeft() + mHorizontalSpacing * i;

      lp.x = width;
      lp.y = height;

      if (lp.verticalSpacing >= 0) {
        verticalSpacing = lp.verticalSpacing;
      }

      width += child.getMeasuredWidth();
      height += verticalSpacing;
    }

    width += getPaddingRight();
    height += getChildAt(getChildCount() - 1).getMeasuredHeight()
        + getPaddingBottom();

    setMeasuredDimension(resolveSize(width, widthMeasureSpec),
        resolveSize(height, heightMeasureSpec));
  }

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

    final int count = getChildCount();
    for (int i = 0; i < count; i++) {
      View child = getChildAt(i);
      LayoutParams lp = (LayoutParams) child.getLayoutParams();

      child.layout(lp.x, lp.y, lp.x + child.getMeasuredWidth(), lp.y
          + child.getMeasuredHeight());
    }
  }

  @Override
  protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
    return p instanceof LayoutParams;
  }

  @Override
  protected LayoutParams generateDefaultLayoutParams() {
    return new LayoutParams(LayoutParams.WRAP_CONTENT,
        LayoutParams.WRAP_CONTENT);
  }

  @Override
  public LayoutParams generateLayoutParams(AttributeSet attrs) {
    return new LayoutParams(getContext(), attrs);
  }

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

  public static class LayoutParams extends ViewGroup.LayoutParams {
    int x;
    int y;
    public int verticalSpacing;

    public LayoutParams(Context context, AttributeSet attrs) {
      super(context, attrs);

      TypedArray a = context.obtainStyledAttributes(attrs,
          R.styleable.CascadeLayout_LayoutParams);
      try {
        verticalSpacing = a
            .getDimensionPixelSize(
                R.styleable.CascadeLayout_LayoutParams_layout_vertical_spacing,
                -1);
      } finally {
        a.recycle();
      }
    }

    public LayoutParams(int w, int h) {
      super(w, h);
    }

  }
}

res/values/dimen.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright (c) 2012 Manning
  See the file license.txt for copying permission.
-->

<resources>
    <dimen name="cascade_horizontal_spacing">10dp</dimen>
    <dimen name="cascade_vertical_spacing">10dp</dimen>
</resources>

res/values/attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright (c) 2012 Manning
  See the file license.txt for copying permission.
-->

<resources>
    <declare-styleable name="CascadeLayout">
        <attr name="horizontal_spacing" format="dimension" />
        <attr name="vertical_spacing" format="dimension" />
    </declare-styleable>

    <declare-styleable name="CascadeLayout_LayoutParams">
        <attr name="layout_vertical_spacing" format="dimension" />
    </declare-styleable>
</resources>

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