微信5.0之Fragment使用

　　相信大家对于微信5.0的切换效果一定很有印象，对于一些童鞋一定认为这是通过TabHost实现的，不过这里我要纠正一下你们的错误观点了，这个效果的实现是通过Fragment+ViewPage实现的，看上去简单的滑动切换，里面包含了很多腾讯工程师对于Android UI设计的独特视角和超强的业务能力，真心为他们点一个赞。说了这么多，下面我们开始探讨如何实现这样炫酷的效果，开始之前建议大家先看一下关于Fragment的介绍，这样会更好的帮助我们理解今天要介绍的知识。

　　我们本篇最后的设计效果：

　　

　　下面我们开始今天的代码解析，让我们一起学习吧。

　　我们项目的目录结构：

　　

　　第一步：创建自定义View实现底部切换按钮

　　对于微信主界面底部有4个类似按钮的小图标，这些小图标会随着我们滑动事件的改变而改变，开始绘制之前我们需要准备4张小图片，为我们接下来的开发做好准备。自定义View的代码：

public class ChangeColorIconWithTextView extends View
{

    private Bitmap mBitmap;
    private Canvas mCanvas;
    private Paint mPaint;
    /**
     * 颜色
     */
    private int mColor = 0xFF45C01A;
    /**
     * 透明度 0.0-1.0
     */
    private float mAlpha = 0f;
    /**
     * 图标
     */
    private Bitmap mIconBitmap;
    /**
     * 限制绘制icon的范围
     */
    private Rect mIconRect;
    /**
     * icon底部文本
     */
    private String mText = "微信";
    private int mTextSize = (int) TypedValue.applyDimension(
            TypedValue.COMPLEX_UNIT_SP, 10, getResources().getDisplayMetrics());
    private Paint mTextPaint;
    private Rect mTextBound = new Rect();

    public ChangeColorIconWithTextView(Context context)
    {
        super(context);
    }

    /**
     * 初始化自定义属性值
     * 
     * @param context
     * @param attrs
     */
    public ChangeColorIconWithTextView(Context context, AttributeSet attrs)
    {
        super(context, attrs);

        // 获取设置的图标
        TypedArray a = context.obtainStyledAttributes(attrs,
                R.styleable.ChangeColorIconView);

        int n = a.getIndexCount();
        for (int i = 0; i < n; i++)
        {

            int attr = a.getIndex(i);
            switch (attr)
            {
            case R.styleable.ChangeColorIconView_icon:
                BitmapDrawable drawable = (BitmapDrawable) a.getDrawable(attr);
                mIconBitmap = drawable.getBitmap();
                break;
            case R.styleable.ChangeColorIconView_color:
                mColor = a.getColor(attr, 0x45C01A);
                break;
            case R.styleable.ChangeColorIconView_text:
                mText = a.getString(attr);
                break;
            case R.styleable.ChangeColorIconView_text_size:
                mTextSize = (int) a.getDimension(attr, TypedValue
                        .applyDimension(TypedValue.COMPLEX_UNIT_SP, 10,
                                getResources().getDisplayMetrics()));
                break;

            }
        }

        a.recycle();

        mTextPaint = new Paint();
        mTextPaint.setTextSize(mTextSize);
        mTextPaint.setColor(0xff555555);
        // 得到text绘制范围
        mTextPaint.getTextBounds(mText, 0, mText.length(), mTextBound);

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        // 得到绘制icon的宽
        int bitmapWidth = Math.min(getMeasuredWidth() - getPaddingLeft()
                - getPaddingRight(), getMeasuredHeight() - getPaddingTop()
                - getPaddingBottom() - mTextBound.height());

        int left = getMeasuredWidth() / 2 - bitmapWidth / 2;
        int top = (getMeasuredHeight() - mTextBound.height()) / 2 - bitmapWidth
                / 2;
        // 设置icon的绘制范围
        mIconRect = new Rect(left, top, left + bitmapWidth, top + bitmapWidth);

    }

    @Override
    protected void onDraw(Canvas canvas)
    {

        int alpha = (int) Math.ceil((255 * mAlpha));
        canvas.drawBitmap(mIconBitmap, null, mIconRect, null);
        setupTargetBitmap(alpha);
        drawSourceText(canvas, alpha);
        drawTargetText(canvas, alpha);
        canvas.drawBitmap(mBitmap, 0, 0, null);

    }
    
    private void setupTargetBitmap(int alpha)
    {
        mBitmap = Bitmap.createBitmap(getMeasuredWidth(), getMeasuredHeight(),
                Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
        mPaint = new Paint();
        mPaint.setColor(mColor);
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setAlpha(alpha);
        mCanvas.drawRect(mIconRect, mPaint);
        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
        mPaint.setAlpha(255);
        mCanvas.drawBitmap(mIconBitmap, null, mIconRect, mPaint);
    }

    private void drawSourceText(Canvas canvas, int alpha)
    {
        mTextPaint.setTextSize(mTextSize);
        mTextPaint.setColor(0xff333333);
        mTextPaint.setAlpha(255 - alpha);
        canvas.drawText(mText, mIconRect.left + mIconRect.width() / 2
                - mTextBound.width() / 2,
                mIconRect.bottom + mTextBound.height(), mTextPaint);
    }
    
    private void drawTargetText(Canvas canvas, int alpha)
    {
        mTextPaint.setColor(mColor);
        mTextPaint.setAlpha(alpha);
        canvas.drawText(mText, mIconRect.left + mIconRect.width() / 2
                - mTextBound.width() / 2,
                mIconRect.bottom + mTextBound.height(), mTextPaint);
        
    }

    public void setIconAlpha(float alpha)
    {
        this.mAlpha = alpha;
        invalidateView();
    }

    private void invalidateView()
    {
        if (Looper.getMainLooper() == Looper.myLooper())
        {
            invalidate();
        } else
        {
            postInvalidate();
        }
    }

    public void setIconColor(int color)
    {
        mColor = color;
    }

    public void setIcon(int resId)
    {
        this.mIconBitmap = BitmapFactory.decodeResource(getResources(), resId);
        if (mIconRect != null)
            invalidateView();
    }

    public void setIcon(Bitmap iconBitmap)
    {
        this.mIconBitmap = iconBitmap;
        if (mIconRect != null)
            invalidateView();
    }

    private static final String INSTANCE_STATE = "instance_state";
    private static final String STATE_ALPHA = "state_alpha";

    @Override
    protected Parcelable onSaveInstanceState()
    {
        Bundle bundle = new Bundle();
        bundle.putParcelable(INSTANCE_STATE, super.onSaveInstanceState());
        bundle.putFloat(STATE_ALPHA, mAlpha);
        return bundle;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state)
    {
        if (state instanceof Bundle)
        {
            Bundle bundle = (Bundle) state;
            mAlpha = bundle.getFloat(STATE_ALPHA);
            super.onRestoreInstanceState(bundle.getParcelable(INSTANCE_STATE));
        } else
        {
            super.onRestoreInstanceState(state);
        }

    }

}

　　第二步：设置自定义属性

　　在我们工程目录values下新建一个attr.xml，用来设置我们的自定义属性：

<?xml version="1.0" encoding="utf-8"?>
<!-- 自定义属性 -->
<resources>

    <attr name="icon" format="reference" />
    <attr name="color" format="color" />
    <attr name="text" format="string" />
    <attr name="text_size" format="dimension" />

    <declare-styleable name="ChangeColorIconView">
        <attr name="icon" />
        <attr name="color" />
        <attr name="text" />
        <attr name="text_size" />
    </declare-styleable>

</resources>

　　第三步：设置一个自定义属性

　　我们的Layout文件夹下新建一个drawable文件夹，在里面新建一个tabbg.xml：

<?xml version="1.0" encoding="utf-8"?>
<!-- 布局文件LinearLayout -->
<shape xmlns:android="http://schemas.android.com/apk/res/android" >
    <stroke android:width="1dp" android:color="#eee" />
    <solid android:color="#F7F7F7"/>
</shape>

　　第四步：设置主界面底部显示的文字

　　打开string.xml添加文字定义：

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">微信</string>
    <string name="tab_weixin">one</string>
    <string name="tab_contact">two</string>
    <string name="tab_find">three</string>
    <string name="tab_me">four</string>

</resources>

　　第五步：布局文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:zhy="http://schemas.android.com/apk/res/com.zhy.weixin6.ui"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <android.support.v4.view.ViewPager
        android:id="@+id/id_viewpager"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1" >
    </android.support.v4.view.ViewPager>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="60dp"
        android:background="@drawable/tabbg"
        android:orientation="horizontal" >

        <com.zhy.weixin6.ui.ChangeColorIconWithTextView
            android:id="@+id/id_indicator_one"
            android:layout_width="0dp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:padding="5dp"
            zhy:icon="@drawable/ic_menu_start_conversation"
            zhy:text="@string/tab_weixin"
            zhy:text_size="12sp" />

        <com.zhy.weixin6.ui.ChangeColorIconWithTextView
            android:id="@+id/id_indicator_two"
            android:layout_width="0dp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:padding="5dp"
            zhy:icon="@drawable/ic_menu_friendslist"
            zhy:text="@string/tab_contact"
            zhy:text_size="12sp" />

        <com.zhy.weixin6.ui.ChangeColorIconWithTextView
            android:id="@+id/id_indicator_three"
            android:layout_width="0dp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:padding="5dp"
            zhy:icon="@drawable/ic_menu_emoticons"
            zhy:text="@string/tab_find"
            zhy:text_size="12sp" />

        <com.zhy.weixin6.ui.ChangeColorIconWithTextView
            android:id="@+id/id_indicator_four"
            android:layout_width="0dp"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:padding="5dp"
            zhy:icon="@drawable/ic_menu_allfriends"
            zhy:text="@string/tab_me"
            zhy:text_size="12sp" />
    </LinearLayout>

</LinearLayout>

　　注意红色标注处xmlns:zhy="http://schemas.android.com/apk/res/com.zhy.weixin6.ui"；com.zhy.weixin6.ui为工程包名。自定义属性的使用通过zhy引用。

　　第六步：我们的Fragment创建

public class oneFragment extends Fragment
{
    private String mTitle = "one";
    

    public oneFragment()
    {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState)
    {
        if (getArguments() != null)
        {
            mTitle = getArguments().getString("title");
        }

        TextView textView = new TextView(getActivity());
        textView.setTextSize(20);
        textView.setBackgroundColor(Color.parseColor("#ffffffff"));
        textView.setGravity(Gravity.CENTER);
        textView.setText(mTitle);
        return textView;
    }
}

　　第七步：主Activity

@SuppressLint("NewApi")
public class MainActivity extends FragmentActivity implements
        OnPageChangeListener, OnClickListener
{
    private ViewPager mViewPager;
    private List<Fragment> mTabs = new ArrayList<Fragment>();
    private FragmentPagerAdapter mAdapter;

    private String[] mTitles = new String[] { "First Fragment!",
            "Second Fragment!", "Third Fragment!", "Fourth Fragment!" };

    private List<ChangeColorIconWithTextView> mTabIndicator = new ArrayList<ChangeColorIconWithTextView>();

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mViewPager = (ViewPager) findViewById(R.id.id_viewpager);

        initDatas();

        mViewPager.setAdapter(mAdapter);
        mViewPager.setOnPageChangeListener(this);
    }

    private void initDatas()
    {

        for (String title : mTitles)
        {
            oneFragment tabFragment = new oneFragment();
            Bundle args = new Bundle();
            args.putString("title", title);
            tabFragment.setArguments(args);
            mTabs.add(tabFragment);
        }
        
        mAdapter = new FragmentPagerAdapter(getSupportFragmentManager())
        {

            @Override
            public int getCount()
            {
                return mTabs.size();
            }

            @Override
            public Fragment getItem(int arg0)
            {
                return mTabs.get(arg0);
            }
        };

        initTabIndicator();

    }

    //初始化按钮，设置点击监听
    private void initTabIndicator()
    {
        ChangeColorIconWithTextView one = (ChangeColorIconWithTextView) findViewById(R.id.id_indicator_one);
        ChangeColorIconWithTextView two = (ChangeColorIconWithTextView) findViewById(R.id.id_indicator_two);
        ChangeColorIconWithTextView three = (ChangeColorIconWithTextView) findViewById(R.id.id_indicator_three);
        ChangeColorIconWithTextView four = (ChangeColorIconWithTextView) findViewById(R.id.id_indicator_four);

        mTabIndicator.add(one);
        mTabIndicator.add(two);
        mTabIndicator.add(three);
        mTabIndicator.add(four);

        one.setOnClickListener(this);
        two.setOnClickListener(this);
        three.setOnClickListener(this);
        four.setOnClickListener(this);

        one.setIconAlpha(1.0f);
    }

    @Override
    //监听滑动事件
    public void onPageSelected(int arg0)
    {
    }

    @Override
    //监听滑动事件
    public void onPageScrolled(int position, float positionOffset,
            int positionOffsetPixels)
    {

        if (positionOffset > 0)
        {
            ChangeColorIconWithTextView left = mTabIndicator.get(position);
            ChangeColorIconWithTextView right = mTabIndicator.get(position + 1);

            left.setIconAlpha(1 - positionOffset);
            right.setIconAlpha(positionOffset);
        }

    }

    @Override
    //监听滑动事件
    public void onPageScrollStateChanged(int state)
    {
    }

    @Override
    //监听点击事件
    public void onClick(View v)
    {

        resetOtherTabs();

        switch (v.getId())
        {
        case R.id.id_indicator_one:
            mTabIndicator.get(0).setIconAlpha(1.0f);
            mViewPager.setCurrentItem(0, false);
            break;
        case R.id.id_indicator_two:
            mTabIndicator.get(1).setIconAlpha(1.0f);
            mViewPager.setCurrentItem(1, false);
            break;
        case R.id.id_indicator_three:
            mTabIndicator.get(2).setIconAlpha(1.0f);
            mViewPager.setCurrentItem(2, false);
            break;
        case R.id.id_indicator_four:
            mTabIndicator.get(3).setIconAlpha(1.0f);
            mViewPager.setCurrentItem(3, false);
            break;

        }

    }

    /**
     * 重置其他的Tab
     */
    private void resetOtherTabs()
    {
        for (int i = 0; i < mTabIndicator.size(); i++)
        {
            mTabIndicator.get(i).setIconAlpha(0);
        }
    }

}

　　到这里我们的微信5.0主界面设计效果就实现完毕，大家可以测试一下，有什么疑问，欢迎留言讨论。下一篇：Fragment使用