Android 自定义控件玩转字体变色 打造炫酷ViewPager指示器

释放双眼,带上耳机,听听看~!

1、概述

本篇博客的产生呢,是因为,群里的哥们暖暖给我发了个效果图,然后问我该如何实现顶部ViewPager指示器的字体变色,该效果图是这样的:

大概是今天头条的app,神奇的地方就在于,切换ViewPager页面的时候,顶部指示器改成了字体颜色的变化,个人觉得还是不错的。

那么核心的地方就是做一个支持字体这样逐渐染色就可以了,我大概想了32s,扫描了一些可能实现的方案,最终定位了一个靠谱的,下面我就带大家开始实现的征程。

实现之前贴一下我们的效果图:

2、效果图

1、简单使用

效果如上图了,关于颜失色的改变我添加了两个方向,一个是左方向,一个是有方向。

单纯的使用,可能觉得没什么意思,下面看结合ViewPager使用的一个例子。

2、结合ViewPager使用

可以看到我们切换页面的时候,上面的指示器的效果,棒棒哒~~~

当然了,学会了原理,你可以扩展,可以做个性的进度条,可以将字体变色改为背景色变色,可以把方向改为上下,太多了,自己去抠脚想把。

3、原理

看完效果图,有木有什么思路~~~花几分钟想想,因为原理很简单~~

我大致想了下,目测绘制半个字估计不行,那么就在绘制范围上下功夫,你可以全部绘制,但是我控制显示的范围,所以上述效果:

其实是绘制了两遍字体,但是呢,分别控制了绘制的显示范围,实现了逐渐变色的效果,那么对于范围的控制,有什么方便的API么,显然是有的

canvas有个clipRect的方法~~~ok,原理分析完毕~~

4、实现

说到实现,那第一步肯定又是自定义属性,我们这里的属性,需要text,textSize,textOriginColor,textChangeColor,progress,大致看一下,应该都能看出来作用吧,看不出来没事,结合下面的代码。tip:我们的View叫做ColorTrackView,感谢小七的命名。

1、自定义属性和获取

attr.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
<attr name="text" format="string" />
<attr name="text_size" format="dimension" />
<attr name="text_origin_color" format="color|reference" />
<attr name="text_change_color" format="color|reference" />
<attr name="progress" format="float" />
<attr name="direction">
<enum name="left" value="0" />
<enum name="right" value="1" />
</attr>
<declare-styleable name="ColorTrackView">
<attr name="text" />
<attr name="text_size" />
<attr name="text_origin_color" />
<attr name="text_change_color" />
<attr name="progress" />
<attr name="direction" />
</declare-styleable>
</resources>

然后在我们的ColorTrackView的构造方法中进行获取这些个渣渣属性:

/**
*
* @author zhy
*
*/
public class ColorTrackView extends View
{
private int mTextStartX;
public enum Direction
{
LEFT , RIGHT ;
}
private int mDirection = DIRECTION_LEFT;
private static final int  DIRECTION_LEFT = 0 ;
private static final int  DIRECTION_RIGHT= 1 ;
public void setDirection(int direction)
{
mDirection = direction;
}
private String mText = "张鸿洋";
private Paint mPaint;
private int mTextSize = sp2px(30);
private int mTextOriginColor = 0xff000000;
private int mTextChangeColor = 0xffff0000;
private Rect mTextBound = new Rect();
private int mTextWidth;
private int mRealWidth;
private float mProgress;
public ColorTrackView(Context context)
{
super(context, null);
}
public ColorTrackView(Context context, AttributeSet attrs)
{
super(context, attrs);
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
TypedArray ta = context.obtainStyledAttributes(attrs,
R.styleable.ColorTrackView);
mText = ta.getString(R.styleable.ColorTrackView_text);
mTextSize = ta.getDimensionPixelSize(
R.styleable.ColorTrackView_text_size, mTextSize);
mTextOriginColor = ta.getColor(
R.styleable.ColorTrackView_text_origin_color,
mTextOriginColor);
mTextChangeColor = ta.getColor(
R.styleable.ColorTrackView_text_change_color,
mTextChangeColor);
mProgress = ta.getFloat(R.styleable.ColorTrackView_progress, 0);
mDirection = ta.getInt(R.styleable.ColorTrackView_direction, mDirection);
ta.recycle();
mPaint.setTextSize(mTextSize);
measureText();
}
private void measureText()
{
mTextWidth = (int) mPaint.measureText(mText);
mPaint.getTextBounds(mText, 0, mText.length(), mTextBound);
}

可以看到我同时贴出了成员变量,大家简单看下就行了,都比较简单。

获取了属性,初始化完成一些成员变量以后,那么应该走向我们的measure之旅了~~

2、onMeasure

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
int width = measureWidth(widthMeasureSpec);
int height = measureHeight(heightMeasureSpec);
setMeasuredDimension(width, height);
mRealWidth = getMeasuredWidth() - getPaddingLeft() - getPaddingRight();
mTextStartX = mRealWidth / 2 - mTextWidth / 2;
}
private int measureHeight(int measureSpec)
{
int mode = MeasureSpec.getMode(measureSpec);
int val = MeasureSpec.getSize(measureSpec);
int result = 0;
switch (mode)
{
case MeasureSpec.EXACTLY:
result = val;
break;
case MeasureSpec.AT_MOST:
case MeasureSpec.UNSPECIFIED:
result = mTextBound.height();
break;
}
result = mode == MeasureSpec.AT_MOST ? Math.min(result, val) : result;
return result + getPaddingTop() + getPaddingBottom();
}
private int measureWidth(int measureSpec)
{
int mode = MeasureSpec.getMode(measureSpec);
int val = MeasureSpec.getSize(measureSpec);
int result = 0;
switch (mode)
{
case MeasureSpec.EXACTLY:
result = val;
break;
case MeasureSpec.AT_MOST:
case MeasureSpec.UNSPECIFIED:
// result = mTextBound.width();
result = mTextWidth;
break;
}
result = mode == MeasureSpec.AT_MOST ? Math.min(result, val) : result;
return result + getPaddingLeft() + getPaddingRight();
}

关于测量,也是比较传统的写法,根据传入的widthMeasureSpec、heightMeasureSpec,利用MeasureSpec分别获取模式和值,如何是EXACTLY万事大吉,如果是AT_MOST、UNSPECIFIED那么就进行自己测量需要的空间,当然了,最好注意如果是AT_MOST不应该大于父类传入的值。

这里提一下,如果偷懒的话,可以选择继承TextView,然后测量就不需要写了,TextView默认帮你实现了,还能利用TextView的一些属性,不过咱们这个例子比较简单,我最终还是选择了继承View,继承View有种everything under control 的感觉。

测量完成以后,不用说都是绘制了。

3、onDraw

@Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
int r = (int) (mProgress* mTextWidth +mTextStartX );
if(mDirection == DIRECTION_LEFT)
{
drawChangeLeft(canvas, r);
drawOriginLeft(canvas, r);
}else
{
drawOriginRight(canvas, r);
drawChangeRight(canvas, r);
}
}
private void drawChangeRight(Canvas canvas, int r)
{
drawText(canvas, mTextChangeColor, (int) (mTextStartX +(1-mProgress)*mTextWidth), mTextStartX+mTextWidth );
}
private void drawOriginRight(Canvas canvas, int r)
{
drawText(canvas, mTextOriginColor, mTextStartX, (int) (mTextStartX +(1-mProgress)*mTextWidth) );
}
private void drawChangeLeft(Canvas canvas, int r)
{
drawText(canvas, mTextChangeColor, mTextStartX, (int) (mTextStartX + mProgress * mTextWidth) );
}
private void drawOriginLeft(Canvas canvas, int r)
{
drawText(canvas, mTextOriginColor, (int) (mTextStartX + mProgress * mTextWidth), mTextStartX +mTextWidth );
}
private void drawText(Canvas canvas , int color , int startX , int endX)
{
mPaint.setColor(color);
canvas.save(Canvas.CLIP_SAVE_FLAG);
canvas.clipRect(startX, 0, endX, getMeasuredHeight());
canvas.drawText(mText, mTextStartX, getMeasuredHeight() / 2
+ mTextBound.height() / 2, mPaint);
canvas.restore();
}

绘制的核心就在于利用mProgress和方向去计算应该clip的范围,具体的参考代码,没什么难点。有了范围以后,无非就是drawText~~~

该View的完整代码:https://www.jishudog.com/26560/html 

主要的方法介绍完毕,我们就该测试了。

5、测试

1、简单测试

布局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:zhy="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<com.zhy.view.ColorTrackView
android:id="@+id/id_changeTextColorView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:background="#44ff0000"
android:padding="10dp"
zhy:progress="0"
zhy:text="张鸿洋"
zhy:text_change_color="#ffff0000"
zhy:text_origin_color="#ff000000"
zhy:text_size="60sp" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="@+id/id_left"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="startLeftChange"
android:text="StartLeft" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/id_left"
android:onClick="startRightChange"
android:text="StartRight" />
</LinearLayout>
</RelativeLayout>

注意我们的自定义属性的命名空间,该布局就一个ColorTrackView,然后两个按钮来控制进度。

SimpleUseActivity:

package com.zhy.viewpagerIndicator;
import android.animation.ObjectAnimator;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import com.zhy.view.ColorTrackView;
public class SimpleUseActivity extends Activity
{
ColorTrackView mView;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_simple_main);
mView = (ColorTrackView) findViewById(R.id.id_changeTextColorView);
}
@SuppressLint("NewApi")
public void startLeftChange(View view)
{
mView.setDirection(0);
ObjectAnimator.ofFloat(mView, "progress", 0, 1).setDuration(2000)
.start();
}
@SuppressLint("NewApi")
public void startRightChange(View view)
{
mView.setDirection(1);
ObjectAnimator.ofFloat(mView, "progress", 0, 1).setDuration(2000)
.start();
}
}

这里拿属性动画进行的测试,没有导入3.0以下兼容包,有需要自己导入。

效果图,见上效果图1。

2、结合ViewPager

布局文件:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:zhy="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:orientation="horizontal" >
<com.zhy.view.ColorTrackView
android:id="@+id/id_tab_01"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
zhy:progress="1"
zhy:text="简介"
zhy:text_change_color="#ffff0000"
zhy:text_origin_color="#ff000000"
zhy:text_size="18sp" />
<com.zhy.view.ColorTrackView
android:id="@+id/id_tab_02"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
zhy:text="评价"
zhy:text_change_color="#ffff0000"
zhy:text_origin_color="#ff000000"
zhy:text_size="18sp" />
<com.zhy.view.ColorTrackView
android:id="@+id/id_tab_03"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
zhy:text="相关"
zhy:text_change_color="#ffff0000"
zhy:text_origin_color="#ff000000"
zhy:text_size="18sp" />
</LinearLayout>
<android.support.v4.view.ViewPager
android:id="@+id/id_viewpager"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" >
</android.support.v4.view.ViewPager>
</LinearLayout>

3个ColorTrackView代表Tab,下面是ViewPager

ViewPagerUseActivity:

package com.zhy.viewpagerIndicator;
import java.util.ArrayList;
import java.util.List;
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.util.Log;
import com.zhy.view.ColorTrackView;
public class ViewPagerUseActivity extends FragmentActivity
{
private String[] mTitles = new String[] { "简介", "评价", "相关" };
private ViewPager mViewPager;
private FragmentPagerAdapter mAdapter;
private TabFragment[] mFragments = new TabFragment[mTitles.length];
private List<ColorTrackView> mTabs = new ArrayList<ColorTrackView>();
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_vp_main);
initViews();
initDatas();
initEvents();
}
private void initEvents()
{
mViewPager.setOnPageChangeListener(new OnPageChangeListener()
{
@Override
public void onPageSelected(int position)
{
}
@Override
public void onPageScrolled(int position, float positionOffset,
int positionOffsetPixels)
{
if (positionOffset > 0)
{
ColorTrackView left = mTabs.get(position);
ColorTrackView right = mTabs.get(position + 1);
left.setDirection(1);
right.setDirection(0);
Log.e("TAG", positionOffset+"");
left.setProgress( 1-positionOffset);
right.setProgress(positionOffset);
}
}
@Override
public void onPageScrollStateChanged(int state)
{
}
});
}
private void initDatas()
{
for (int i = 0; i < mTitles.length; i++)
{
mFragments[i] = (TabFragment) TabFragment.newInstance(mTitles[i]);
}
mAdapter = new FragmentPagerAdapter(getSupportFragmentManager())
{
@Override
public int getCount()
{
return mTitles.length;
}
@Override
public Fragment getItem(int position)
{
return mFragments[position];
}
};
mViewPager.setAdapter(mAdapter);
mViewPager.setCurrentItem(0);
}
private void initViews()
{
mViewPager = (ViewPager) findViewById(R.id.id_viewpager);
mTabs.add((ColorTrackView) findViewById(R.id.id_tab_01));
mTabs.add((ColorTrackView) findViewById(R.id.id_tab_02));
mTabs.add((ColorTrackView) findViewById(R.id.id_tab_03));
}
}

TabFragment

package com.zhy.viewpagerIndicator;
import java.util.Random;
import android.graphics.Color;
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.TextView;
public class TabFragment extends Fragment
{
public static final String TITLE = "title";
private String mTitle = "Defaut Value";
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
if (getArguments() != null)
{
mTitle = getArguments().getString(TITLE);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
TextView tv = new TextView(getActivity());
tv.setTextSize(60);
Random r = new Random();
tv.setBackgroundColor(Color.argb(r.nextInt(120), r.nextInt(255),
r.nextInt(255), r.nextInt(255)));
tv.setText(mTitle);
tv.setGravity(Gravity.CENTER);
return tv;
}
public static TabFragment newInstance(String title)
{
TabFragment tabFragment = new TabFragment();
Bundle bundle = new Bundle();
bundle.putString(TITLE, title);
tabFragment.setArguments(bundle);
return tabFragment;
}
}

效果图见上效果图2。

 

源码地址: ColorTrackView,欢迎star or fork。

 

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