仿微信页面切换图标颜色渐变效果

主要是提供一种思路，一般来书，类似效果无非就是在Canvas，Paint，Drawable等绘图类里搞来搞去。如果对绘图类比较熟悉的话，基本就没问题了，尤其游戏开发者。
我是记录一下，以后可以照抄了，具体见原帖：
http://blog.csdn.net/lmj623565791/article/details/41087219

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.os.Looper;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.util.TypedValue;
import android.view.View;

public class ChangeColorIconWithTextView extends View {

	private Bitmap mBitmap;
	private Canvas mCanvas;
	private Paint mPaint;
	/**
	 * 选中的颜色
	 */
	private int mColor = 0xFFFF0000;
	/**
	 * 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, 12,
			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);
		}

	}

}

自定义属性：

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

使用：

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewConfiguration;
import android.view.Window;

@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);

		setOverflowShowingAlways();
		getActionBar().setDisplayShowHomeEnabled(false);
		mViewPager = (ViewPager) findViewById(R.id.id_viewpager);

		initDatas();

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

	private void initDatas()
	{

		for (String title : mTitles)
		{
			TabFragment tabFragment = new TabFragment();
			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();

	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu)
	{
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	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
	public void onPageSelected(int arg0)
	{
	}

	@Override
	public void onPageScrolled(int position, float positionOffset,
			int positionOffsetPixels)
	{
		// Log.e("TAG", "position = " + position + " , positionOffset = "
		// + positionOffset);

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

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

	}

	@Override
	public void onPageScrollStateChanged(int state)
	{

	}

	@Override
	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);
		}
	}

	@Override
	public boolean onMenuOpened(int featureId, Menu menu)
	{
		if (featureId == Window.FEATURE_ACTION_BAR && menu != null)
		{
			if (menu.getClass().getSimpleName().equals("MenuBuilder"))
			{
				try
				{
					Method m = menu.getClass().getDeclaredMethod(
							"setOptionalIconsVisible", Boolean.TYPE);
					m.setAccessible(true);
					m.invoke(menu, true);
				} catch (Exception e)
				{
				}
			}
		}
		return super.onMenuOpened(featureId, menu);
	}

	private void setOverflowShowingAlways()
	{
		try
		{
			// true if a permanent menu key is present, false otherwise.
			ViewConfiguration config = ViewConfiguration.get(this);
			Field menuKeyField = ViewConfiguration.class
					.getDeclaredField("sHasPermanentMenuKey");
			menuKeyField.setAccessible(true);
			menuKeyField.setBoolean(config, false);
		} catch (Exception e)
		{
			e.printStackTrace();
		}
	}

}

布局：

<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>

同样的效果：
http://www.open-open.com/lib/view/open1473666409185.html

一个优质的新闻客户端app
http://www.itlanbao.com/code/20151126/10000/100663.html