Android-滑动解锁高亮文字自定义TextView

public class HightLightTextView extends TextView {

    // 存储view的宽度
    private int mTextViewWidth = 0;
    // 画笔
    private Paint mPaint;
    // 线性渲染
    private LinearGradient mLinearGradient;
    // 存储变换的matrix
    private Matrix matrix;
    // 移动距离
    private int mTranslateX = 0;

    // 构造方法
    public HightLightTextView(Context context) {
        this(context, null);
    }

    public HightLightTextView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public HightLightTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    /**
     * view的调用过程:构造方法->onFinishInflate->onSizeChanged->onDraw
     */
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        // 获取view的宽度，初始化画笔等初始属性
        if (mTextViewWidth == 0) {
            mTextViewWidth = getMeasuredWidth();
            // 如果宽度大于0的话，则初始化
            if (mTextViewWidth > 0) {
                // 初始化画笔
                mPaint = getPaint();
                // 线性渲染
                mLinearGradient = new LinearGradient(0, getMeasuredHeight(), mTextViewWidth, 0,
                        new int[]{0X55FFFFFF, 0XFFFFFFFF, 0X55FFFFFF},
                        new float[]{0, 0.5f, 1}, Shader.TileMode.CLAMP);
                mPaint.setShader(mLinearGradient);
                matrix = new Matrix();
            }
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (matrix != null) {
            mTranslateX += mTextViewWidth / 10;
            // 如果移动的距离大于两倍的宽度，则重新开始移动
            if (mTranslateX > 2 * mTextViewWidth) {
                mTranslateX = -mTextViewWidth;
            }
            // 平移matrix
            matrix.setTranslate(mTranslateX, 0);
            // 设置线性变化的matrix
            mLinearGradient.setLocalMatrix(matrix);
            // 延迟50ms重绘  (重绘时会重新调用onDraw)
            postInvalidateDelayed(50);
        }
    }

}