一个类似于android启动界面的动画效果

package com.example.android; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.LinearGradient; import android.graphics.Matrix; import android.graphics.Paint; import android.graphics.Shader; import android.graphics.Shader.TileMode; import android.util.AttributeSet; import android.view.View; public class MaskedTextView extends View{ private Paint txtPaint; private Shader shader; private float dx=50; private long lastTime = System.currentTimeMillis(); private boolean start = false; private void init(){ txtPaint = new Paint(); txtPaint.setColor(Color.GRAY); txtPaint.setAntiAlias(true); txtPaint.setTextSize(26); shader = new LinearGradient(0, 0, 200, 0, new int[]{Color.argb(255, 120, 120, 120), Color.argb(255, 120, 120, 120), Color.WHITE}, new float[]{0, 0.7f, 1}, TileMode.MIRROR); txtPaint.setShader(shader); } public MaskedTextView(Context context) { super(context); init(); } public MaskedTextView(Context context, AttributeSet attrs){ super(context, attrs); init(); } public void setStart(boolean start) { this.start = start; invalidate(); } @Override protected void onDraw(Canvas canvas) { long now = System.currentTimeMillis(); float elapsed = (now - lastTime)/4.5f; dx += elapsed; Matrix matrix = new Matrix(); if(start){ matrix.setTranslate(dx, 0); invalidate(); }else{ matrix.setTranslate(0, 0); } shader.setLocalMatrix(matrix); canvas.drawText(getContext().getString(R.string.msg), 0, 25, txtPaint); lastTime = now; } }