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[转载]android-Viewpager – 一个人的ye – 博客频道 – CSDN.NET.
ViewPager是google SDk中自带的一个附加包的一个类（在Android-compatibility这个文件夹下），可以用来实现屏幕间的切换。
如可以仿一个workspace的效果。
Actviity:
import com.viewpagerindicator.CirclePageIndicator;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
public class ViewpagerActivity extends FragmentActivity {
TestFragmentAdapter mAdapter;
ViewPager mPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//The look of this sample is set via a style in the manifest
setContentView(R.layout.simple_circles);
mAdapter = new TestFragmentAdapter(getSupportFragmentManager());
mPager = (ViewPager)findViewById(R.id.pager);
mPager.setAdapter(mAdapter);
CirclePageIndicator indicator = (CirclePageIndicator)findViewById(R.id.indicator);
indicator.setViewPager(mPager);
}
}
simple_circles.xml:
<!--?xml version="1.0" encoding="utf-8"?-->
TestFragmentAdapter:
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
class TestFragmentAdapter extends FragmentPagerAdapter {
protected static final String[] CONTENT = new String[] { "第一页", "第二页", "第三页", "第四页", };
private int mCount = CONTENT.length;
public TestFragmentAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
return TestFragment.newInstance(CONTENT[position % CONTENT.length]);
}
@Override
public int getCount() {
return mCount;
}
public void setCount(int count) {
if (count > 0 && count <= 10) {
mCount = count;
notifyDataSetChanged();
}
}
}
TestFragment:
package com.shao.pager;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;
import android.widget.TextView;
public final class TestFragment extends Fragment {
private static final String KEY_CONTENT = "TestFragment:Content";
public static TestFragment newInstance(String content) {
TestFragment fragment = new TestFragment();
fragment.mContent = content;
return fragment;
}
private String mContent = "???";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if ((savedInstanceState != null) && savedInstanceState.containsKey(KEY_CONTENT)) {
mContent = savedInstanceState.getString(KEY_CONTENT);
}
TextView text = new TextView(getActivity());
text.setGravity(Gravity.CENTER);
text.setText(mContent);
text.setTextSize(20 * getResources().getDisplayMetrics().density);
text.setPadding(20, 20, 20, 20);
LinearLayout layout = new LinearLayout(getActivity());
layout.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
layout.setGravity(Gravity.CENTER);
layout.addView(text);
return layout;
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString(KEY_CONTENT, mContent);
}
}
PageIndicator:
package com.viewpagerindicator;
import android.support.v4.view.ViewPager;
public interface PageIndicator extends ViewPager.OnPageChangeListener {
public void setViewPager(ViewPager view);
public void setViewPager(ViewPager view, int initialPosition);
public void setCurrentItem(int item);
public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener);
}
CliclePageIndicator:
package com.viewpagerindicator;
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.Paint.Style;
import android.os.Parcel;
import android.os.Parcelable;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import com.shao.pager.R;
public class CirclePageIndicator extends View implements PageIndicator {
public static final int HORIZONTAL = 0;
public static final int VERTICAL = 1;
private float mRadius;
private final Paint mPaintStroke;
private final Paint mPaintFill;
private ViewPager mViewPager;
private ViewPager.OnPageChangeListener mListener;
private int mCurrentPage;
private int mSnapPage;
private int mCurrentOffset;
private int mScrollState;
private int mPageSize;
private int mOrientation;
private boolean mCentered;
private boolean mSnap;
public CirclePageIndicator(Context context) {
this(context, null);
}
public CirclePageIndicator(Context context, AttributeSet attrs) {
this(context, attrs, R.attr.circlePageIndicatorStyle);
}
public CirclePageIndicator(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
//Load defaults from resources
final Resources res = getResources();
final int defaultFillColor = res.getColor(R.color.default_circle_indicator_fill_color);
final int defaultOrientation = res.getInteger(R.integer.default_circle_indicator_orientation);
final int defaultStrokeColor = res.getColor(R.color.default_circle_indicator_stroke_color);
final float defaultStrokeWidth = res.getDimension(R.dimen.default_circle_indicator_stroke_width);
final float defaultRadius = res.getDimension(R.dimen.default_circle_indicator_radius);
final boolean defaultCentered = res.getBoolean(R.bool.default_circle_indicator_centered);
final boolean defaultSnap = res.getBoolean(R.bool.default_circle_indicator_snap);
//Retrieve styles attributes
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CirclePageIndicator, defStyle, R.style.Widget_CirclePageIndicator);
mCentered = a.getBoolean(R.styleable.CirclePageIndicator_centered, defaultCentered);
mOrientation = a.getInt(R.styleable.CirclePageIndicator_orientation, defaultOrientation);
mPaintStroke = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaintStroke.setStyle(Style.STROKE);
mPaintStroke.setColor(a.getColor(R.styleable.CirclePageIndicator_strokeColor, defaultStrokeColor));
mPaintStroke.setStrokeWidth(a.getDimension(R.styleable.CirclePageIndicator_strokeWidth, defaultStrokeWidth));
mPaintFill = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaintFill.setStyle(Style.FILL);
mPaintFill.setColor(a.getColor(R.styleable.CirclePageIndicator_fillColor, defaultFillColor));
mRadius = a.getDimension(R.styleable.CirclePageIndicator_radius, defaultRadius);
mSnap = a.getBoolean(R.styleable.CirclePageIndicator_snap, defaultSnap);
a.recycle();
}
public void setCentered(boolean centered) {
mCentered = centered;
invalidate();
}
public boolean isCentered() {
return mCentered;
}
public void setFillColor(int fillColor) {
mPaintFill.setColor(fillColor);
invalidate();
}
public int getFillColor() {
return mPaintFill.getColor();
}
public void setOrientation(int orientation) {
switch (orientation) {
case HORIZONTAL:
case VERTICAL:
mOrientation = orientation;
updatePageSize();
requestLayout();
break;
default:
throw new IllegalArgumentException("Orientation must be either HORIZONTAL or VERTICAL.");
}
}
public int getOrientation() {
return mOrientation;
}
public void setStrokeColor(int strokeColor) {
mPaintStroke.setColor(strokeColor);
invalidate();
}
public int getStrokeColor() {
return mPaintStroke.getColor();
}
public void setStrokeWidth(float strokeWidth) {
mPaintStroke.setStrokeWidth(strokeWidth);
invalidate();
}
public float getStrokeWidth() {
return mPaintStroke.getStrokeWidth();
}
public void setRadius(float radius) {
mRadius = radius;
invalidate();
}
public float getRadius() {
return mRadius;
}
public void setSnap(boolean snap) {
mSnap = snap;
invalidate();
}
public boolean isSnap() {
return mSnap;
}
/*
* (non-Javadoc)
*
* @see android.view.View#onDraw(android.graphics.Canvas)
*/
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int longSize;
int longPaddingBefore;
int longPaddingAfter;
int shortPaddingBefore;
if (mOrientation == HORIZONTAL) {
longSize = getWidth();
longPaddingBefore = getPaddingLeft();
longPaddingAfter = getPaddingRight();
shortPaddingBefore = getPaddingTop();
} else {
longSize = getHeight();
longPaddingBefore = getPaddingTop();
longPaddingAfter = getPaddingBottom();
shortPaddingBefore = getPaddingLeft();
}
final int count = mViewPager.getAdapter().getCount();
final float threeRadius = mRadius * 3;
final float shortOffset = shortPaddingBefore + mRadius;
float longOffset = longPaddingBefore + mRadius;
if (mCentered) {
longOffset += ((longSize - longPaddingBefore - longPaddingAfter) / 2.0f) - ((count * threeRadius) / 2.0f);
}
float dX;
float dY;
//Draw stroked circles
for (int iLoop = 0; iLoop < count; iLoop++) { float drawLong = longOffset + (iLoop * threeRadius); if (mOrientation == HORIZONTAL) { dX = drawLong; dY = shortOffset; } else { dX = shortOffset; dY = drawLong; } canvas.drawCircle(dX, dY, mRadius, mPaintStroke); } //Draw the filled circle according to the current scroll float cx = (mSnap ? mSnapPage : mCurrentPage) * threeRadius; if (!mSnap && (mPageSize != 0)) { cx += (mCurrentOffset * 1.0f / mPageSize) * threeRadius; } if (mOrientation == HORIZONTAL) { dX = longOffset + cx; dY = shortOffset; } else { dX = shortOffset; dY = longOffset + cx; } canvas.drawCircle(dX, dY, mRadius, mPaintFill); } @Override public boolean onTouchEvent(MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN) { final int count = mViewPager.getAdapter().getCount(); final int longSize = (mOrientation == HORIZONTAL) ? getWidth() : getHeight(); final float halfLongSize = longSize / 2; final float halfCircleLongSize = (count * 3 * mRadius) / 2; final float pointerValue = (mOrientation == HORIZONTAL) ? event.getX() : event.getY(); if ((mCurrentPage > 0) && (pointerValue < halfLongSize - halfCircleLongSize)) {
setCurrentItem(mCurrentPage - 1);
return true;
} else if ((mCurrentPage < count - 1) && (pointerValue > halfLongSize + halfCircleLongSize)) {
setCurrentItem(mCurrentPage + 1);
return true;
}
}
return super.onTouchEvent(event);
}
@Override
public void setViewPager(ViewPager view) {
if (view.getAdapter() == null) {
throw new IllegalStateException("ViewPager does not have adapter instance.");
}
mViewPager = view;
mViewPager.setOnPageChangeListener(this);
updatePageSize();
invalidate();
}
private void updatePageSize() {
if (mViewPager != null) {
mPageSize = (mOrientation == HORIZONTAL) ? mViewPager.getWidth() : mViewPager.getHeight();
}
}
@Override
public void setViewPager(ViewPager view, int initialPosition) {
setViewPager(view);
setCurrentItem(initialPosition);
}
@Override
public void setCurrentItem(int item) {
if (mViewPager == null) {
throw new IllegalStateException("ViewPager has not been bound.");
}
mViewPager.setCurrentItem(item);
mCurrentPage = item;
invalidate();
}
@Override
public void onPageScrollStateChanged(int state) {
mScrollState = state;
if (mListener != null) {
mListener.onPageScrollStateChanged(state);
}
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
mCurrentPage = position;
mCurrentOffset = positionOffsetPixels;
updatePageSize();
invalidate();
if (mListener != null) {
mListener.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
}
@Override
public void onPageSelected(int position) {
if (mSnap || mScrollState == ViewPager.SCROLL_STATE_IDLE) {
mCurrentPage = position;
mSnapPage = position;
invalidate();
}
if (mListener != null) {
mListener.onPageSelected(position);
}
}
@Override
public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) {
mListener = listener;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
if (mOrientation == HORIZONTAL) {
setMeasuredDimension(measureLong(widthMeasureSpec), measureShort(heightMeasureSpec));
} else {
setMeasuredDimension(measureShort(widthMeasureSpec), measureLong(heightMeasureSpec));
}
}
/**
* 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 measureLong(int measureSpec) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
if (specMode == MeasureSpec.EXACTLY) {
//We were told how big to be
result = specSize;
} else {
//Calculate the width according the views count
final int count = mViewPager.getAdapter().getCount();
result = (int)(getPaddingLeft() + getPaddingRight()
+ (count * 2 * mRadius) + (count - 1) * mRadius + 1);
//Respect AT_MOST value if that was what is called for by measureSpec
if (specMode == MeasureSpec.AT_MOST) {
result = Math.min(result, specSize);
}
}
return result;
}
private int measureShort(int measureSpec) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
if (specMode == MeasureSpec.EXACTLY) {
//We were told how big to be
result = specSize;
} else {
//Measure the height
result = (int)(2 * mRadius + getPaddingTop() + getPaddingBottom() + 1);
//Respect AT_MOST value if that was what is called for by measureSpec
if (specMode == MeasureSpec.AT_MOST) {
result = Math.min(result, specSize);
}
}
return result;
}
@Override
public void onRestoreInstanceState(Parcelable state) {
SavedState savedState = (SavedState)state;
super.onRestoreInstanceState(savedState.getSuperState());
mCurrentPage = savedState.currentPage;
mSnapPage = savedState.currentPage;
requestLayout();
}
@Override
public Parcelable onSaveInstanceState() {
Parcelable superState = super.onSaveInstanceState();
SavedState savedState = new SavedState(superState);
savedState.currentPage = mCurrentPage;
return savedState;
}
static class SavedState extends BaseSavedState {
int currentPage;
public SavedState(Parcelable superState) {
super(superState);
}
private SavedState(Parcel in) {
super(in);
currentPage = in.readInt();
}
@Override
public void writeToParcel(Parcel dest, int flags) {
super.writeToParcel(dest, flags);
dest.writeInt(currentPage);
}
public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {
@Override
public SavedState createFromParcel(Parcel in) {
return new SavedState(in);
}
@Override
public SavedState[] newArray(int size) {
return new SavedState[size];
}
};
}
}
