Java tutorial
/* * Copyright (C) 2013 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 org.bottiger.podcast.views.SlidingTab; import android.R; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.support.v4.content.ContextCompat; import android.util.AttributeSet; import android.view.View; import android.widget.LinearLayout; class SlidingTabStrip extends LinearLayout { private static final int DEFAULT_BOTTOM_BORDER_THICKNESS_DIPS = 2; private static final byte DEFAULT_BOTTOM_BORDER_COLOR_ALPHA = 0x26; private static final int SELECTED_INDICATOR_THICKNESS_DIPS = 4; private static final int DEFAULT_SELECTED_INDICATOR_COLOR = 0xFF33B5E5; private static final int DEFAULT_DIVIDER_THICKNESS_DIPS = 1; private static final byte DEFAULT_DIVIDER_COLOR_ALPHA = 0x20; private static final float DEFAULT_DIVIDER_HEIGHT = 0.5f; private final int mBottomBorderThickness; private final Paint mBottomBorderPaint; private final int mSelectedIndicatorThickness; private final Paint mSelectedIndicatorPaint; private final int mDefaultBottomBorderColor; private final Paint mDividerPaint; private final float mDividerHeight; private int mSelectedPosition; private float mSelectionOffset; private SlidingTabLayout.TabColorizer mCustomTabColorizer; private final SimpleTabColorizer mDefaultTabColorizer; SlidingTabStrip(Context context) { this(context, null); } SlidingTabStrip(Context context, AttributeSet attrs) { super(context, attrs); setWillNotDraw(false); final float density = getResources().getDisplayMetrics().density; final int themeForegroundColor = ContextCompat.getColor(context, R.color.white); mDefaultBottomBorderColor = setColorAlpha(themeForegroundColor, DEFAULT_BOTTOM_BORDER_COLOR_ALPHA); mDefaultTabColorizer = new SimpleTabColorizer(); mDefaultTabColorizer.setIndicatorColors(DEFAULT_SELECTED_INDICATOR_COLOR); mDefaultTabColorizer.setDividerColors(setColorAlpha(themeForegroundColor, DEFAULT_DIVIDER_COLOR_ALPHA)); mBottomBorderThickness = (int) (DEFAULT_BOTTOM_BORDER_THICKNESS_DIPS * density); mBottomBorderPaint = new Paint(); mBottomBorderPaint.setColor(mDefaultBottomBorderColor); mSelectedIndicatorThickness = (int) (SELECTED_INDICATOR_THICKNESS_DIPS * density); mSelectedIndicatorPaint = new Paint(); mDividerHeight = DEFAULT_DIVIDER_HEIGHT; mDividerPaint = new Paint(); mDividerPaint.setStrokeWidth((int) (DEFAULT_DIVIDER_THICKNESS_DIPS * density)); } void setCustomTabColorizer(SlidingTabLayout.TabColorizer customTabColorizer) { mCustomTabColorizer = customTabColorizer; invalidate(); } void setSelectedIndicatorColors(int... colors) { // Make sure that the custom colorizer is removed mCustomTabColorizer = null; mDefaultTabColorizer.setIndicatorColors(colors); invalidate(); } void setDividerColors(int... colors) { // Make sure that the custom colorizer is removed mCustomTabColorizer = null; mDefaultTabColorizer.setDividerColors(colors); invalidate(); } void onViewPagerPageChanged(int position, float positionOffset) { mSelectedPosition = position; mSelectionOffset = positionOffset; invalidate(); } @Override protected void onDraw(Canvas canvas) { final int height = getHeight(); final int childCount = getChildCount(); final int dividerHeightPx = (int) (Math.min(Math.max(0f, mDividerHeight), 1f) * height); final SlidingTabLayout.TabColorizer tabColorizer = mCustomTabColorizer != null ? mCustomTabColorizer : mDefaultTabColorizer; // Thick colored underline below the current selection if (childCount > 0) { View selectedTitle = getChildAt(mSelectedPosition); int left = selectedTitle.getLeft(); int right = selectedTitle.getRight(); int color = tabColorizer.getIndicatorColor(mSelectedPosition); if (mSelectionOffset > 0f && mSelectedPosition < (getChildCount() - 1)) { int nextColor = tabColorizer.getIndicatorColor(mSelectedPosition + 1); if (color != nextColor) { color = blendColors(nextColor, color, mSelectionOffset); } // Draw the selection partway between the tabs View nextTitle = getChildAt(mSelectedPosition + 1); left = (int) (mSelectionOffset * nextTitle.getLeft() + (1.0f - mSelectionOffset) * left); right = (int) (mSelectionOffset * nextTitle.getRight() + (1.0f - mSelectionOffset) * right); } mSelectedIndicatorPaint.setColor(color); canvas.drawRect(left, height - mSelectedIndicatorThickness, right, height, mSelectedIndicatorPaint); } // Thin underline along the entire bottom edge canvas.drawRect(0, height - mBottomBorderThickness, getWidth(), height, mBottomBorderPaint); // Vertical separators between the titles int separatorTop = (height - dividerHeightPx) / 2; for (int i = 0; i < childCount - 1; i++) { View child = getChildAt(i); mDividerPaint.setColor(tabColorizer.getDividerColor(i)); canvas.drawLine(child.getRight(), separatorTop, child.getRight(), separatorTop + dividerHeightPx, mDividerPaint); } } /** * Set the alpha value of the {@code color} to be the given {@code alpha} value. */ private static int setColorAlpha(int color, byte alpha) { return Color.argb(alpha, Color.red(color), Color.green(color), Color.blue(color)); } /** * Blend {@code color1} and {@code color2} using the given ratio. * * @param ratio of which to blend. 1.0 will return {@code color1}, 0.5 will give an even blend, * 0.0 will return {@code color2}. */ private static int blendColors(int color1, int color2, float ratio) { final float inverseRation = 1f - ratio; float r = (Color.red(color1) * ratio) + (Color.red(color2) * inverseRation); float g = (Color.green(color1) * ratio) + (Color.green(color2) * inverseRation); float b = (Color.blue(color1) * ratio) + (Color.blue(color2) * inverseRation); return Color.rgb((int) r, (int) g, (int) b); } private static class SimpleTabColorizer implements SlidingTabLayout.TabColorizer { private int[] mIndicatorColors; private int[] mDividerColors; @Override public final int getIndicatorColor(int position) { return mIndicatorColors[position % mIndicatorColors.length]; } @Override public final int getDividerColor(int position) { return mDividerColors[position % mDividerColors.length]; } void setIndicatorColors(int... colors) { mIndicatorColors = colors; } void setDividerColors(int... colors) { mDividerColors = colors; } } }