如何使用viewpager与fragment写一个app导航activity
时间：2014-05-18 18:28:18
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今天我们来看一下如何使用viewpager和fragment组合来写一个app导航activity，这里使用到了android开源控件viewpagerindicator，有兴趣的同学可以去它网站上看看它的介绍。
附上效果截图一张：
demo中只有一个activity，是用activity_main.xml来布局，其内容如下：
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
<com.example.circlepageindicator.view.CirclePageIndicator
android:id="@+id/indicator"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:padding="20dip" />
</FrameLayout>在这里有一个自定义的View，名字叫做CirclePageIndicator，我们看一下它的定义：
/*
* Copyright (C) 2011 Patrik Akerfeldt
* Copyright (C) 2011 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 com.example.circlepageindicator.view;
import static android.graphics.Paint.ANTI_ALIAS_FLAG;
import static android.widget.LinearLayout.HORIZONTAL;
import static android.widget.LinearLayout.VERTICAL;
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.graphics.drawable.Drawable;
import android.os.Parcel;
import android.os.Parcelable;
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 com.example.circlepageindicator.R;
/**
* Draws circles (one for each view). The current view position is filled and
* others are only stroked.
*/
public class CirclePageIndicator extends View implements PageIndicator {
private static final int INVALID_POINTER = -1;
private float mRadius;
private final Paint mPaintPageFill = new Paint(ANTI_ALIAS_FLAG);
private final Paint mPaintStroke = new Paint(ANTI_ALIAS_FLAG);
private final Paint mPaintFill = new Paint(ANTI_ALIAS_FLAG);
private ViewPager mViewPager;
private ViewPager.OnPageChangeListener mListener;
private int mCurrentPage;
private int mSnapPage;
private float mPageOffset;
private int mScrollState;
private int mOrientation;
private boolean mCentered;
private boolean mSnap;
private int mTouchSlop;
private float mLastMotionX = -1;
private int mActivePointerId = INVALID_POINTER;
private boolean mIsDragging;
public CirclePageIndicator(Context context) {
this(context, null);
}
public CirclePageIndicator(Context context, AttributeSet attrs) {
this(context, attrs, R.attr.vpiCirclePageIndicatorStyle);
}
public CirclePageIndicator(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
if (isInEditMode()) return;
//Load defaults from resources
final Resources res = getResources();
final int defaultPageColor = res.getColor(R.color.default_circle_indicator_page_color);
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, 0);
mCentered = a.getBoolean(R.styleable.CirclePageIndicator_centered, defaultCentered);
mOrientation = a.getInt(R.styleable.CirclePageIndicator_android_orientation, defaultOrientation);
mPaintPageFill.setStyle(Style.FILL);
mPaintPageFill.setColor(a.getColor(R.styleable.CirclePageIndicator_pageColor, defaultPageColor));
mPaintStroke.setStyle(Style.STROKE);
mPaintStroke.setColor(a.getColor(R.styleable.CirclePageIndicator_strokeColor, defaultStrokeColor));
mPaintStroke.setStrokeWidth(a.getDimension(R.styleable.CirclePageIndicator_strokeWidth, defaultStrokeWidth));
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);
Drawable background = a.getDrawable(R.styleable.CirclePageIndicator_android_background);
if (background != null) {
setBackgroundDrawable(background);
}
a.recycle();
final ViewConfiguration configuration = ViewConfiguration.get(context);
mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);
}
public void setCentered(boolean centered) {
mCentered = centered;
invalidate();
}
public boolean isCentered() {
return mCentered;
}
public void setPageColor(int pageColor) {
mPaintPageFill.setColor(pageColor);
invalidate();
}
public int getPageColor() {
return mPaintPageFill.getColor();
}
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;
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;
}
@Override
protected void onDraw(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;
}
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 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;
float pageFillRadius = mRadius;
if (mPaintStroke.getStrokeWidth() > 0) {
pageFillRadius -= mPaintStroke.getStrokeWidth() / 2.0f;
}
//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;
}
// Only paint fill if not completely transparent
if (mPaintPageFill.getAlpha() > 0) {
canvas.drawCircle(dX, dY, pageFillRadius, mPaintPageFill);
}
// Only paint stroke if a stroke width was non-zero
if (pageFillRadius != mRadius) {
canvas.drawCircle(dX, dY, mRadius, mPaintStroke);
}
}
//Draw the filled circle according to the current scroll
float cx = (mSnap ? mSnapPage : mCurrentPage) * threeRadius;
if (!mSnap) {
cx += mPageOffset * threeRadius;
}
if (mOrientation == HORIZONTAL) {
dX = longOffset + cx;
dY = shortOffset;
} else {
dX = shortOffset;
dY = longOffset + cx;
}
canvas.drawCircle(dX, dY, mRadius, mPaintFill);
}
public boolean onTouchEvent(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
public void setViewPager(ViewPager view) {
if (mViewPager == view) {
return;
}
if (mViewPager != null) {
mViewPager.setOnPageChangeListener(null);
}
if (view.getAdapter() == null) {
throw new IllegalStateException("ViewPager does not have adapter instance.");
}
//将参数view传递给类变量mViewPager
mViewPager = view;
//为mViewPager设置页面改变监听器
mViewPager.setOnPageChangeListener(this);
//使当前view设置的属性有效
invalidate();
}
@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.");
}
//设置当前显示第几个页面
mViewPager.setCurrentItem(item);
mCurrentPage = item;
invalidate();
}
@Override
public void notifyDataSetChanged() {
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;
mPageOffset = positionOffset;
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) {
//将参数listener传递给类变量mListener
mListener = listener;
}
/*
* (non-Javadoc)
*
* 设置当前视图的宽度和高度
*
* @see android.view.View#onMeasure(int, int)
*/
@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;
int specMode = MeasureSpec.getMode(measureSpec);
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 = (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;
}
/**
* 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 measureShort(int measureSpec) {
int result;
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);
}
@SuppressWarnings("UnusedDeclaration")
public static final Creator<SavedState> CREATOR = new Creator<SavedState>() {
@Override
public SavedState createFromParcel(Parcel in) {
return new SavedState(in);
}
@Override
public SavedState[] newArray(int size) {
return new SavedState[size];
}
};
}
}
这个视图是继承自View，然后实现PageIndicator接口，先来看一下PageIndicator接口的定义，然后接着分析CirclePageIndicator。
/*
* Copyright (C) 2011 Patrik Akerfeldt
* Copyright (C) 2011 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 com.example.circlepageindicator.view;
import android.support.v4.view.ViewPager;
/**
* A PageIndicator is responsible to show an visual indicator on the total views
* number and the current visible view.
*/
public interface PageIndicator extends ViewPager.OnPageChangeListener {
/**
* Bind the indicator to a ViewPager.
*
* @param view
*/
void setViewPager(ViewPager view);
/**
* Bind the indicator to a ViewPager.
*
* @param view
* @param initialPosition
*/
void setViewPager(ViewPager view, int initialPosition);
/**
* <p>
* Set the current page of both the ViewPager and indicator.
* </p>
*
* <p>
* This <strong>must</strong> be used if you need to set the page before the
* views are drawn on screen (e.g., default start page).
* </p>
*
* @param item
*/
void setCurrentItem(int item);
/**
* Set a page change listener which will receive forwarded events.
*
* @param listener
*/
void setOnPageChangeListener(ViewPager.OnPageChangeListener listener);
/**
* Notify the indicator that the fragment list has changed.
*/
void notifyDataSetChanged();
}
每一个方法都有详细的解释，这五个方法CirclePageIndicator必须要实现，主要工作是设置viewpager传递进来的方法，设置显示第几个页面的方法，然后重写实现onPageChangedListener的三个回调方法，另外，这个视图控件最重要的两个方法就是onDraw()方法和onMeasure()方法，onDraw()方法里面定义了画几个空心圈，然后再在哪个地方画一个实心圈，onMeasure()方法里面告诉android我这个控件需要的宽度和高度。
接着我们来看一下TestFragmentAdapter的定义，这是为ViewPager提供数据的类，最关键的方法就是getItem(int position)这个方法，这个方法返回的fragment对象填充ViewPager的每个Page，我们来看一下TestFragmentAdapter的定义如下：
package com.example.circlepageindicator;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import com.example.circlepageindicator.view.IconPagerAdapter;
class TestFragmentAdapter extends FragmentPagerAdapter implements
IconPagerAdapter {
private int mCount = CONTENT.length;
protected static final int[] CONTENT = new int[] { R.drawable.guide_350_01,
R.drawable.guide_350_02, R.drawable.guide_350_03,
R.drawable.guide_350_04 };
public TestFragmentAdapter(FragmentManager fm) {
super(fm);
}
/**
* 最重要的方法,返回viewpager中所有的子fragment
*/
@Override
public Fragment getItem(int position) {
return TestFragment.newInstance(CONTENT[position % CONTENT.length]);
}
@Override
public int getCount() {
return mCount;
}
@Override
public CharSequence getPageTitle(int position) {
return null;
}
@Override
public int getIconResId(int index) {
return 0;
}
public void setCount(int count) {
if (count > 0 && count <= 10) {
mCount = count;
notifyDataSetChanged();
}
}
}我们再来看下TestFragment的定义，这个类定义了每个Fragment是什么样子，最重要的方法是onCreateView()，这个方法返回的对象view就是fragment里面的视图，它告诉我们这个fragment应该长什么样子。以下是TestFragment的定义：
package com.example.circlepageindicator;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;
public final class TestFragment extends Fragment {
private static final String KEY_CONTENT = "TestFragment:Content";
public static TestFragment newInstance(int content) {
TestFragment fragment = new TestFragment();
fragment.mContent = content;
return fragment;
}
private int mContent;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if ((savedInstanceState != null) && savedInstanceState.containsKey(KEY_CONTENT)) {
mContent = savedInstanceState.getInt(KEY_CONTENT);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
LinearLayout layout = new LinearLayout(getActivity());
layout.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
layout.setBackgroundResource(mContent);
return layout;
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(KEY_CONTENT, mContent);
}
}
好，前期准备都完成了，我们现在只需要在activity中初始化一下就ok了，下面是MyActivity的定义：
package com.example.circlepageindicator;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.view.Window;
import com.example.circlepageindicator.view.CirclePageIndicator;
public class MyActivity extends BaseSampleActivity {
/**
* Called when the activity is first created.
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
mAdapter = new TestFragmentAdapter(getSupportFragmentManager());
mPager = (ViewPager)findViewById(R.id.viewpager);
mPager.setAdapter(mAdapter);
mIndicator = (CirclePageIndicator)findViewById(R.id.indicator);
mIndicator.setViewPager(mPager);
}
}
最后奉上完整的源码：
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