Android 自定义TextView实现文字渐变动画

柔光的暖阳◎ 2022-06-11 09:51 790阅读 0赞

效果图:

![155007_4C1U_2256215.gif][]

代码：

import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.LinearGradient;
    import android.graphics.Matrix;
    import android.graphics.Paint;
    import android.graphics.Shader;
    import android.util.AttributeSet;
    import android.widget.TextView;
    
    /** * Created by Administrator on 2017/8/4. */ public class MyTextView extends TextView {
        private LinearGradient mLinearGradient;
        private Matrix mGradientMatrix;
        private Paint mPaint;
        private int mViewWidth = 0;
        private int mTranslate = 0;
    
        private boolean mAnimating = true;
        private int delta = 15;
        public MyTextView(Context ctx)
        {
            this(ctx,null);
        }
    
        public MyTextView(Context context, AttributeSet attrs) {
            super(context, attrs);
        }
    
        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
            if (mViewWidth == 0) {
                mViewWidth = getMeasuredWidth();
                if (mViewWidth > 0) {
                    mPaint = getPaint();
                    String text = getText().toString();
                    // float textWidth = mPaint.measureText(text);
                    int size;
                    if(text.length()>0)
                    {
                        size = mViewWidth*2/text.length();
                    }else{
                        size = mViewWidth;
                    }
                    mLinearGradient = new LinearGradient(-size, 0, 0, 0,
                            new int[] { 0x33ffffff, 0xffffffff, 0x33ffffff },
                            new float[] { 0, 0.5f, 1 }, Shader.TileMode.CLAMP); //边缘融合
                    mPaint.setShader(mLinearGradient);
                    mGradientMatrix = new Matrix();
                }
            }
        }
    
        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
    
            int length = Math.max(length(), 1);
            if (mAnimating && mGradientMatrix != null) {
                float mTextWidth = getPaint().measureText(getText().toString());
                mTranslate += delta;
                if (mTranslate > mTextWidth+1 || mTranslate<1) {
                    delta  = -delta;
                }
                mGradientMatrix.setTranslate(mTranslate, 0);
                mLinearGradient.setLocalMatrix(mGradientMatrix);
                postInvalidateDelayed(30);
            }
        }
    
    }

[155007_4C1U_2256215.gif]: /images/20220611/6fb0e86e856c4bdcaa6e66c54ead4b08.png