<TextView

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:shadowColor="#ff0000"

        android:shadowDx="3"

        android:shadowDy="3"

        android:shadowRadius="1"

        android:text="abcdefg"

        android:textColor="#0000ff"

        android:textSize="100sp" />

android:shadowRadius="0"

android:shadowRadius="20"

        android:shadowDx="30"

        android:shadowDy="30"

package com.example.imagetest;

import android.R.integer;

import android.app.Activity;

import android.graphics.drawable.Drawable;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.TextView;

public class MainActivity extends Activity {

    TextView tv;

    Button bt;

    int a;

    float t1;

    float t2;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        tv = (TextView) findViewById(R.id.tv);

        bt = (Button) findViewById(R.id.bt);

        a = 0;

        t1 = getResources().getDimension(R.dimen.activity_horizontal_margin);

        t2 = getResources().getDimension(R.dimen.activity_vertical_margin);

        bt.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View arg0) {

                if (a == 1) {

                    // R.color没有效果

                    tv.setShadowLayer(t1, t1, t1, R.color.aaa);

                    a = 0;

                } else {

                    tv.setShadowLayer(t2, t2, t2, 0x800000ff);

                    a = 1;

                }

                bt.setText(a + "");

            }

        });

    }

}

setShadowLayer(radius, dx, dy, color)；