Android自定义View实现不同朝向字体变色

实现效果：
1.一个文字两种颜色
2.实现不同朝向
3.结合ViewPager
思路：TextView可行？系统提供的只能够显示一种颜色，需要自定义View
extends TextView：onMeasure()不需要实现 textColor颜色，textSize字体大小会少很多逻辑。
1.一个文字两种颜色 画
2.能够从左到右，从右到左
3.整合到ViewPager，监听滚动事件

自定义属性，不变化的颜色 originColor 变化的颜色 changeColor

x要在这个位置

就等于宽度的一半减去文字的一半。

实现一个文字两种颜色

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:paddingBottom="16dp"android:paddingLeft="16dp"android:paddingRight="16dp"android:paddingTop="16dp"><com.example.customview.customview.colortrack.ColorTrackTextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Hello World!"android:textSize="20sp"/></RelativeLayout>

public class ColorTrackTextView extends TextView {//实现一个文字两种颜色---绘制不变色字体的画笔private Paint mOriginPaint;//实现一个文字两种颜色---绘制变色字体的画笔private Paint mChangePaint;//实现一个文字两种颜色--当前的进度private float mCurrentProgress=0.5f;public ColorTrackTextView(Context context) {this(context,null);}public ColorTrackTextView(Context context, @Nullable @org.jetbrains.annotations.Nullable AttributeSet attrs) {this(context, attrs,0);}public ColorTrackTextView(Context context, @Nullable @org.jetbrains.annotations.Nullable AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);initPaint(context,attrs);}//初始化画笔private void initPaint(Context context, AttributeSet attrs) {TypedArray array=context.obtainStyledAttributes(attrs, R.styleable.ColorTrackTextView);int originColor=array.getColor(R.styleable.ColorTrackTextView_originColor, Color.RED);int changeColor=array.getColor(R.styleable.ColorTrackTextView_changeColor,Color.BLUE);mOriginPaint=getPaintByColor(originColor);mChangePaint=getPaintByColor(changeColor);//回收array.recycle();}//根据颜色获取画笔private Paint getPaintByColor(int color){Paint paint=new Paint();//设置颜色paint.setColor(color);//设置抗锯齿paint.setAntiAlias(true);//防抖动paint.setDither(true);//设置字体的大小 就是TextView的字体大小，通过继承TextView可以直接拿paint.setTextSize(getTextSize());return paint;}@Overrideprotected void onDraw(Canvas canvas) {//因为是继承TextView，所以不进行super不然TextView会去画文字
//        super.onDraw(canvas);//canvas.clipRect()  裁剪区域//根据进度把中间值算出来int middle=(int) (mCurrentProgress*getWidth());drawText(canvas,mOriginPaint,0,middle);//绘制变色drawText(canvas,mChangePaint,middle,getWidth());}//1.个文字两种颜色//利用clipRect的API 可以裁剪 左边用一个画笔去画  右边用另一个画笔去画  不断的改变中间值 从而实现变化颜色效果public void drawText(Canvas canvas,Paint paint,int start,int end){//因为要调两次drawText如果不对画布进行save和restore的话，画布只会展示第一次调用的画笔canvas.save();//根据进度把中间值算出来String text=getText().toString();Rect bounds=new Rect();//clipRect裁剪区域,左--上---右---下canvas.clipRect(start,0,end,getHeight());paint.getTextBounds(text,0,text.length(),bounds);//获取字体的宽度int x=getWidth()/2-bounds.width()/2;//基线baseLinePaint.FontMetricsInt fontMetrics=paint.getFontMetricsInt();//bottom是正的.top是负的int dy=(fontMetrics.bottom-fontMetrics.top)/2-fontMetrics.bottom;int baseLine=getHeight()/2+dy;canvas.drawText(text,x,baseLine,paint);canvas.restore();}}

不同朝向

点击按钮实现不同朝向的变色

public class ColorTrackTextView extends TextView {//1.实现一个文字两种颜色---绘制不变色字体的画笔private Paint mOriginPaint;//1.实现一个文字两种颜色---绘制变色字体的画笔private Paint mChangePaint;//1.实现一个文字两种颜色--当前的进度private float mCurrentProgress=0.0f;//2.实现不同的朝向private Direction mDirection =Direction.LEFT_TO_RIGHT;public enum Direction{LEFT_TO_RIGHT,RIGHT_TO_LEFT}public ColorTrackTextView(Context context) {this(context,null);}public ColorTrackTextView(Context context, @Nullable  AttributeSet attrs) {this(context, attrs,0);}public ColorTrackTextView(Context context, @Nullable  AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);initPaint(context,attrs);}//初始化画笔private void initPaint(Context context, AttributeSet attrs) {TypedArray array=context.obtainStyledAttributes(attrs, R.styleable.ColorTrackTextView);int originColor=array.getColor(R.styleable.ColorTrackTextView_originColor, Color.BLACK);int changeColor=array.getColor(R.styleable.ColorTrackTextView_changeColor,Color.BLACK);mOriginPaint=getPaintByColor(originColor);mChangePaint=getPaintByColor(changeColor);//回收array.recycle();}//根据颜色获取画笔private Paint getPaintByColor(int color){Paint paint=new Paint();//设置颜色paint.setColor(color);//设置抗锯齿paint.setAntiAlias(true);//防抖动paint.setDither(true);//设置字体的大小 就是TextView的字体大小，通过继承TextView可以直接拿paint.setTextSize(getTextSize());return paint;}@Overrideprotected void onDraw(Canvas canvas) {//因为是继承TextView，所以不进行super不然TextView会去画文字
//        super.onDraw(canvas);//canvas.clipRect()  裁剪区域//根据进度把中间值算出来int middle=(int) (mCurrentProgress*getWidth());//从左变到右if(mDirection == Direction.LEFT_TO_RIGHT){   //左边是红色右边是黑色drawText(canvas,mChangePaint,0,middle);//绘制变色drawText(canvas,mOriginPaint,middle,getWidth());}else {//从右到左drawText(canvas,mChangePaint,getWidth()-middle,getWidth());//右边是红色左边是黑色//绘制变色drawText(canvas,mOriginPaint,0,getWidth()-middle);}}//1.个文字两种颜色//利用clipRect的API 可以裁剪 左边用一个画笔去画  右边用另一个画笔去画  不断的改变中间值 从而实现变化颜色效果public void drawText(Canvas canvas,Paint paint,int start,int end){//因为要调两次drawText如果不对画布进行save和restore的话，画布只会展示第一次调用的画笔canvas.save();//根据进度把中间值算出来String text=getText().toString();Rect bounds=new Rect();//clipRect裁剪区域,左--上---右---下canvas.clipRect(start,0,end,getHeight());paint.getTextBounds(text,0,text.length(),bounds);//获取字体的宽度int x=getWidth()/2-bounds.width()/2;//基线baseLinePaint.FontMetricsInt fontMetrics=paint.getFontMetricsInt();//bottom是正的.top是负的int dy=(fontMetrics.bottom-fontMetrics.top)/2-fontMetrics.bottom;int baseLine=getHeight()/2+dy;canvas.drawText(text,x,baseLine,paint);canvas.restore();}public void setDirection(Direction direction){this.mDirection=direction;}public void setCurrentProgress(float currentProgress){this.mCurrentProgress = currentProgress;invalidate();}}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"android:paddingBottom="16dp"android:paddingLeft="16dp"android:paddingRight="16dp"android:paddingTop="16dp"><com.example.customview.customview.colortrack.ColorTrackTextViewandroid:id="@+id/color_track_tv"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Hello World!"android:textSize="20sp"app:changeColor="@color/red"app:originColor="@color/black"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="左到右"android:id="@+id/leftToRight"android:onClick="leftToRight"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="右到左"android:onClick="rightToLeft"/></LinearLayout>

结合ViewPager

LinearLayout（代码添加变色的View）+ViewPager
主要代码如下：

public class ViewPagerActivity extends AppCompatActivity {private String[] items ={"直播","推荐","视频","图片","段子","精华"};private LinearLayout mIndicatorContainer;//变成通用的private List<ColorTrackTextView> mIndicators;private ViewPager mViewPager;private String TAG = "ViewPagerActivity";@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_view_pager);mIndicators = new ArrayList<>();mIndicatorContainer = (LinearLayout) findViewById(R.id.indicator_view);mViewPager = (ViewPager) findViewById(R.id.view_pager);initIndicator();initViewPager();}private void initViewPager() {mViewPager.setAdapter(new FragmentPagerAdapter(getSupportFragmentManager()) {@Overridepublic Fragment getItem(int position) {return ItemFragment.newInstance(items[position]);}@Overridepublic int getCount() {return items.length;}});mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {@Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {//position 当前的位置//positionOffset 滚动偏移量 代表滚动的 0 - 1百分比ColorTrackTextView left = mIndicators.get(position);left.setDirection(ColorTrackTextView.Direction.RIGHT_TO_LEFT);left.setCurrentProgress(1-positionOffset);try {ColorTrackTextView right = mIndicators.get(position+1);right.setDirection(ColorTrackTextView.Direction.LEFT_TO_RIGHT);right.setCurrentProgress(positionOffset);}catch (IndexOutOfBoundsException e){}}@Overridepublic void onPageSelected(int position) {}@Overridepublic void onPageScrollStateChanged(int state) {}});}/*** 初始化可变色的指示器*/private void initIndicator() {for(int i=0;i<items.length;i++){//动态添加颜色跟踪的TextViewLinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);params.weight=1;ColorTrackTextView colorTrackTextView = new ColorTrackTextView(this);//设置颜色colorTrackTextView.setTextSize(20);colorTrackTextView.setChangeColor(Color.RED);colorTrackTextView.setText(items[i]);colorTrackTextView.setLayoutParams(params);//把新的加入LinearLayout容器mIndicatorContainer.addView(colorTrackTextView);//加入集合mIndicators.add(colorTrackTextView);}}}

public class ItemFragment extends Fragment {public static ItemFragment newInstance(String item){ItemFragment itemFragment =new ItemFragment();Bundle bundle = new Bundle();bundle.putString("title",item);itemFragment.setArguments(bundle);return itemFragment;}@Overridepublic View onCreateView(@NonNull LayoutInflater inflater, @Nullable  ViewGroup container, @Nullable  Bundle savedInstanceState) {View view = inflater.inflate(R.layout.fragment_item,null);TextView tv=(TextView) view.findViewById(R.id.text);Bundle bundle = getArguments();tv.setText(bundle.getString("title"));return view;}
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"android:gravity="center"><TextViewandroid:id="@+id/text"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="111" /></LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:id="@+id/indicator_view"android:orientation="horizontal"android:paddingTop="10dp"android:paddingBottom="10dp"/><androidx.viewpager.widget.ViewPagerandroid:layout_width="match_parent"android:layout_height="0dp"android:id="@+id/view_pager"android:layout_weight="1"/>
</LinearLayout>