Android实现背景颜色滑动渐变效果的全过程

    //获取屏幕高度
     private float getScreenHeight(){
         DisplayMetrics metric = new DisplayMetrics();
         getWindowManager().getDefaultDisplay().getMetrics(metric);
         int width = metric.widthPixels;     // 屏幕宽度（像素）
         int height = metric.heightPixels;   // 屏幕高度（像素)
         return  height;
     }

  GradientDrawable aDrawable = new GradientDrawable(GradientDrawable.Orientation.TOP_BOTTOM,
                    new int[]{Color.parseColor("#ffffff"), Color.parseColor("#009966"),Color.parseColor("#00ff00")});
            ll_base.setBackground(aDrawable);

   //得到控件的高度与屏幕高度的比例
    private float getScreenHeightScale(int height){
        return height/getScreenHeight();
    }

public class BaseActivity extends Activity {
    private LinearLayout ll_base;
    private int heights;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_base);
        initView();
    }


    private void initView() {
        ll_base = (LinearLayout) findViewById(R.id.ll_base);
    }



    @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN)
    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);

        heights = ll_base.getMeasuredHeight();
        float coloramount=getScreenHeightScale(heights);
        if (coloramount>=0&&coloramount<1.5f){
            GradientDrawable aDrawable = new GradientDrawable(GradientDrawable.Orientation.TOP_BOTTOM,
                    new int[]{Color.parseColor("#ffffff"), Color.parseColor("#009966")});
            ll_base.setBackground(aDrawable);
        }
        if (coloramount>=1.5f&&coloramount<3.0f){
            GradientDrawable aDrawable = new GradientDrawable(GradientDrawable.Orientation.TOP_BOTTOM,
                    new int[]{Color.parseColor("#ffffff"), Color.parseColor("#009966"), Color.parseColor("#00ff00")});
            ll_base.setBackground(aDrawable);
        }
        if (coloramount>=3.0f&&coloramount<4.5f){
            GradientDrawable aDrawable = new GradientDrawable(GradientDrawable.Orientation.TOP_BOTTOM,
                    new int[]{Color.parseColor("#ffffff"), Color.parseColor("#009966"), Color.parseColor("#00ff00"),Color.parseColor("#000000")});
            ll_base.setBackground(aDrawable);
        }
       // .................
    }

    //得到控件的高度与屏幕高度的比例
    private float getScreenHeightScale(int height){
        return height/getScreenHeight();
    }
     //获取屏幕高度
     private float getScreenHeight(){
         DisplayMetrics metric = new DisplayMetrics();
         getWindowManager().getDefaultDisplay().getMetrics(metric);
         int width = metric.widthPixels;     // 屏幕宽度（像素）
         int height = metric.heightPixels;   // 屏幕高度（像素)
         return  height;
     }
}