Java tutorial
/* * Copyright (C) 2012 Jake Wharton * * 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.mariotaku.twidere.view; import android.content.Context; import android.content.res.Resources; import android.content.res.TypedArray; import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.drawable.Drawable; import android.os.Parcel; import android.os.Parcelable; import android.support.annotation.NonNull; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.ViewConfigurationCompat; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import org.mariotaku.twidere.R; import org.mariotaku.twidere.util.support.ViewSupport; import org.mariotaku.twidere.view.iface.PagerIndicator; /** * Draws a line for each page. The current page line is colored differently than * the unselected page lines. */ public class LinePageIndicator extends View implements PagerIndicator { private static final int INVALID_POINTER = -1; private int mActivePointerId = INVALID_POINTER; private final Paint mPaintUnselected = new Paint(Paint.ANTI_ALIAS_FLAG); private final Paint mPaintSelected = new Paint(Paint.ANTI_ALIAS_FLAG); private ViewPager mViewPager; private ViewPager.OnPageChangeListener mListener; private int mCurrentPage; private boolean mCentered; private float mLineWidth; private float mGapWidth; private int mTouchSlop; private float mLastMotionX = -1; private boolean mIsDragging; public LinePageIndicator(final Context context) { this(context, null); } public LinePageIndicator(final Context context, final AttributeSet attrs) { super(context, attrs, 0); if (isInEditMode()) return; final Resources res = getResources(); // Load defaults from resources final int defaultSelectedColor = res.getColor(R.color.default_line_indicator_selected_color); final int defaultUnselectedColor = res.getColor(R.color.default_line_indicator_unselected_color); final float defaultLineWidth = res.getDimension(R.dimen.default_line_indicator_line_width); final float defaultGapWidth = res.getDimension(R.dimen.default_line_indicator_gap_width); final float defaultStrokeWidth = res.getDimension(R.dimen.default_line_indicator_stroke_width); final boolean defaultCentered = res.getBoolean(R.bool.default_line_indicator_centered); // Retrieve styles attributes final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.LinePageIndicator, 0, 0); mCentered = a.getBoolean(R.styleable.LinePageIndicator_centered, defaultCentered); mLineWidth = a.getDimension(R.styleable.LinePageIndicator_lineWidth, defaultLineWidth); mGapWidth = a.getDimension(R.styleable.LinePageIndicator_gapWidth, defaultGapWidth); setStrokeWidth(a.getDimension(R.styleable.LinePageIndicator_strokeWidth, defaultStrokeWidth)); mPaintUnselected .setColor(a.getColor(R.styleable.LinePageIndicator_unselectedColor, defaultUnselectedColor)); mPaintSelected.setColor(a.getColor(R.styleable.LinePageIndicator_selectedColor, defaultSelectedColor)); final Drawable background = a.getDrawable(R.styleable.LinePageIndicator_android_background); if (background != null) { ViewSupport.setBackground(this, background); } a.recycle(); final ViewConfiguration configuration = ViewConfiguration.get(context); mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration); } public float getGapWidth() { return mGapWidth; } public void setGapWidth(final float gapWidth) { mGapWidth = gapWidth; invalidate(); } public float getLineWidth() { return mLineWidth; } public void setLineWidth(final float lineWidth) { mLineWidth = lineWidth; invalidate(); } public int getSelectedColor() { return mPaintSelected.getColor(); } public void setSelectedColor(final int selectedColor) { mPaintSelected.setColor(selectedColor); invalidate(); } public float getStrokeWidth() { return mPaintSelected.getStrokeWidth(); } @SuppressWarnings("SuspiciousNameCombination") public void setStrokeWidth(final float lineHeight) { mPaintSelected.setStrokeWidth(lineHeight); mPaintUnselected.setStrokeWidth(lineHeight); invalidate(); } public int getUnselectedColor() { return mPaintUnselected.getColor(); } public void setUnselectedColor(final int unselectedColor) { mPaintUnselected.setColor(unselectedColor); invalidate(); } public boolean isCentered() { return mCentered; } public void setCentered(final boolean centered) { mCentered = centered; invalidate(); } @Override public void notifyDataSetChanged() { invalidate(); } @Override public void setCurrentItem(final int item) { if (mViewPager == null) throw new IllegalStateException("ViewPager has not been bound."); mViewPager.setCurrentItem(item); mCurrentPage = item; invalidate(); } @Override public void setOnPageChangeListener(final ViewPager.OnPageChangeListener listener) { mListener = listener; } @Override public void setViewPager(final ViewPager viewPager) { if (mViewPager == viewPager) return; if (mViewPager != null) { // Clear us from the old pager. mViewPager.setOnPageChangeListener(null); } if (viewPager.getAdapter() == null) throw new IllegalStateException("ViewPager does not have adapter instance."); mViewPager = viewPager; mViewPager.setOnPageChangeListener(this); invalidate(); } @Override public void setViewPager(final ViewPager view, final int initialPosition) { setViewPager(view); setCurrentItem(initialPosition); } @Override public void onPageScrolled(final int position, final float positionOffset, final int positionOffsetPixels) { if (mListener != null) { mListener.onPageScrolled(position, positionOffset, positionOffsetPixels); } } @Override public void onPageSelected(final int position) { mCurrentPage = position; invalidate(); if (mListener != null) { mListener.onPageSelected(position); } } @Override public void onPageScrollStateChanged(final int state) { if (mListener != null) { mListener.onPageScrollStateChanged(state); } } @Override public boolean onTouchEvent(@NonNull final android.view.MotionEvent ev) { if (super.onTouchEvent(ev)) return true; if (mViewPager == null || mViewPager.getAdapter().getCount() == 0) return false; final int action = ev.getAction() & MotionEventCompat.ACTION_MASK; switch (action) { case MotionEvent.ACTION_DOWN: mActivePointerId = MotionEventCompat.getPointerId(ev, 0); mLastMotionX = ev.getX(); break; case MotionEvent.ACTION_MOVE: { final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId); final float x = MotionEventCompat.getX(ev, activePointerIndex); final float deltaX = x - mLastMotionX; if (!mIsDragging) { if (Math.abs(deltaX) > mTouchSlop) { mIsDragging = true; } } if (mIsDragging) { mLastMotionX = x; if (mViewPager.isFakeDragging() || mViewPager.beginFakeDrag()) { mViewPager.fakeDragBy(deltaX); } } break; } case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: if (!mIsDragging) { final int count = mViewPager.getAdapter().getCount(); final int width = getWidth(); final float halfWidth = width / 2f; final float sixthWidth = width / 6f; if (mCurrentPage > 0 && ev.getX() < halfWidth - sixthWidth) { if (action != MotionEvent.ACTION_CANCEL) { mViewPager.setCurrentItem(mCurrentPage - 1); } return true; } else if (mCurrentPage < count - 1 && ev.getX() > halfWidth + sixthWidth) { if (action != MotionEvent.ACTION_CANCEL) { mViewPager.setCurrentItem(mCurrentPage + 1); } return true; } } mIsDragging = false; mActivePointerId = INVALID_POINTER; if (mViewPager.isFakeDragging()) { mViewPager.endFakeDrag(); } break; case MotionEventCompat.ACTION_POINTER_DOWN: { final int index = MotionEventCompat.getActionIndex(ev); mLastMotionX = MotionEventCompat.getX(ev, index); mActivePointerId = MotionEventCompat.getPointerId(ev, index); break; } case MotionEventCompat.ACTION_POINTER_UP: final int pointerIndex = MotionEventCompat.getActionIndex(ev); final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex); if (pointerId == mActivePointerId) { final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex); } mLastMotionX = MotionEventCompat.getX(ev, MotionEventCompat.findPointerIndex(ev, mActivePointerId)); break; } return true; } @Override protected void onDraw(final Canvas canvas) { super.onDraw(canvas); if (mViewPager == null) return; final int count = mViewPager.getAdapter().getCount(); if (count == 0) return; if (mCurrentPage >= count) { setCurrentItem(count - 1); return; } final float lineWidthAndGap = mLineWidth + mGapWidth; final float indicatorWidth = count * lineWidthAndGap - mGapWidth; final float paddingTop = getPaddingTop(); final float paddingLeft = getPaddingLeft(); final float paddingRight = getPaddingRight(); final float verticalOffset = paddingTop + (getHeight() - paddingTop - getPaddingBottom()) / 2.0f; float horizontalOffset = paddingLeft; if (mCentered) { horizontalOffset += (getWidth() - paddingLeft - paddingRight) / 2.0f - indicatorWidth / 2.0f; } // Draw stroked circles for (int i = 0; i < count; i++) { final float dx1 = horizontalOffset + i * lineWidthAndGap; final float dx2 = dx1 + mLineWidth; canvas.drawLine(dx1, verticalOffset, dx2, verticalOffset, i == mCurrentPage ? mPaintSelected : mPaintUnselected); } } @Override public Parcelable onSaveInstanceState() { final Parcelable superState = super.onSaveInstanceState(); final SavedState savedState = new SavedState(superState); savedState.currentPage = mCurrentPage; return savedState; } @Override public void onRestoreInstanceState(final Parcelable state) { final SavedState savedState = (SavedState) state; super.onRestoreInstanceState(savedState.getSuperState()); mCurrentPage = savedState.currentPage; requestLayout(); } @Override protected void onMeasure(final int widthMeasureSpec, final int heightMeasureSpec) { setMeasuredDimension(measureWidth(widthMeasureSpec), measureHeight(heightMeasureSpec)); } /** * Determines the height of this view * * @param measureSpec A measureSpec packed into an int * @return The height of the view, honoring constraints from measureSpec */ private int measureHeight(final int measureSpec) { float result; final int specMode = MeasureSpec.getMode(measureSpec); final int specSize = MeasureSpec.getSize(measureSpec); if (specMode == MeasureSpec.EXACTLY) { // We were told how big to be result = specSize; } else { // Measure the height result = mPaintSelected.getStrokeWidth() + getPaddingTop() + getPaddingBottom(); // Respect AT_MOST value if that was what is called for by // measureSpec if (specMode == MeasureSpec.AT_MOST) { result = Math.min(result, specSize); } } return (int) Math.ceil(result); } /** * Determines the width of this view * * @param measureSpec A measureSpec packed into an int * @return The width of the view, honoring constraints from measureSpec */ private int measureWidth(final int measureSpec) { float result; final int specMode = MeasureSpec.getMode(measureSpec); final int specSize = MeasureSpec.getSize(measureSpec); if (specMode == MeasureSpec.EXACTLY || mViewPager == null) { // We were told how big to be result = specSize; } else { // Calculate the width according the views count final int count = mViewPager.getAdapter().getCount(); result = getPaddingLeft() + getPaddingRight() + count * mLineWidth + (count - 1) * mGapWidth; // Respect AT_MOST value if that was what is called for by // measureSpec if (specMode == MeasureSpec.AT_MOST) { result = Math.min(result, specSize); } } return (int) Math.ceil(result); } static class SavedState extends BaseSavedState { public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() { @Override public SavedState createFromParcel(final Parcel in) { return new SavedState(in); } @Override public SavedState[] newArray(final int size) { return new SavedState[size]; } }; int currentPage; public SavedState(final Parcelable superState) { super(superState); } private SavedState(final Parcel in) { super(in); currentPage = in.readInt(); } @Override public void writeToParcel(@NonNull final Parcel dest, final int flags) { super.writeToParcel(dest, flags); dest.writeInt(currentPage); } } }