废话少说:

• 先来看下Interpolator的api文档
  (不用翻墙)
      
  上面的图可以看出,Interpolator是一个接口,最根本的接口是TimeInterpolator,下面已经有实现的子类,可以直接拿来用

1.  先加速后减速
2.   一直加速
3.   先向后在向前
4.  结束后弹跳一会
5.   常量值的改变

• 使用官方的类:    
  这里实现以上的5个类,剩下的你们自行体会,图片是一个android logo 先来看效果:
  
  MainActivity:

  package com.huangzhibo.interpolator;import android.media.Image;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.view.animation.AccelerateDecelerateInterpolator;import android.view.animation.AccelerateInterpolator;import android.view.animation.Animation;import android.view.animation.AnticipateInterpolator;import android.view.animation.BounceInterpolator;import android.view.animation.Interpolator;import android.view.animation.LinearInterpolator;import android.view.animation.TranslateAnimation;import android.widget.ImageView;public class MainActivity extends AppCompatActivity {    private ImageView img;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        img= (ImageView) findViewById(R.id.imageView);    }    public void btn(View view){        switch (view.getId()){            case R.id.btn_01:                startAnimator(new AccelerateDecelerateInterpolator());                break;            case R.id.btn_02:                startAnimator(new AccelerateInterpolator());                break;            case R.id.btn_03:                startAnimator(new AnticipateInterpolator());                break;            case R.id.btn_04:                startAnimator(new BounceInterpolator());                break;            case R.id.btn_05:                startAnimator(new LinearInterpolator());                break;        }    }    private void startAnimator(Interpolator interpolator){        Animation animation=new TranslateAnimation(0,500,0,0);        animation.setInterpolator(interpolator);        animation.setDuration(3000);        img.setAnimation(animation);        img.startAnimation(animation);    }}

  到这里相信你已经会使用官方提供的Interpolator类,那么如何自定义自己的Interpolator类呢?

• 从源码入手:

  InterPolator:
  
  什么也没有,好吧,接着看TImeInterPolator->
  
  终于看到曙光了<getInterPolation> 在这里我想我们要实现的方法就是它了.我们可以看下Interpolator的子类->从  下手
   

  public class AccelerateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {    private final float mFactor;    private final double mDoubleFactor;    public AccelerateInterpolator() {        mFactor = 1.0f;        mDoubleFactor = 2.0;    }    /**     * Constructor     *     * @param factor Degree to which the animation should be eased. Seting     *        factor to 1.0f produces a y=x^2 parabola. Increasing factor above     *        1.0f  exaggerates the ease-in effect (i.e., it starts even     *        slower and ends evens faster)     */    public AccelerateInterpolator(float factor) {        mFactor = factor;        mDoubleFactor = 2 * mFactor;    }    public AccelerateInterpolator(Context context, AttributeSet attrs) {        this(context.getResources(), context.getTheme(), attrs);    }    /** @hide */    public AccelerateInterpolator(Resources res, Theme theme, AttributeSet attrs) {        TypedArray a;        if (theme != null) {            a = theme.obtainStyledAttributes(attrs, R.styleable.AccelerateInterpolator, 0, 0);        } else {            a = res.obtainAttributes(attrs, R.styleable.AccelerateInterpolator);        }        mFactor = a.getFloat(R.styleable.AccelerateInterpolator_factor, 1.0f);        mDoubleFactor = 2 * mFactor;        setChangingConfiguration(a.getChangingConfigurations());        a.recycle();    }    public float getInterpolation(float input) {        if (mFactor == 1.0f) {            return input * input;        } else {            return (float)Math.pow(input, mDoubleFactor);        }    }    /** @hide */    @Override    public long createNativeInterpolator() {        return NativeInterpolatorFactoryHelper.createAccelerateInterpolator(mFactor);    }

  开始分析:三个构造函数 我们来看下只有一个参数的构造函数里面的赋值式子和

   

  return (float)Math.pow(input, mDoubleFactor);

        看到没,Math.pow(a,b)函数->是求a的b次方的,那如何改变它的值,不断变大改变速率呢,这里自定义Interpolator,打印log看getInterPolation是不是多次调用就知道了

package com.huangzhibo.interpolator;import android.util.Log;import android.view.animation.Interpolator;/** * Created by HuangZhiBo on 2017/3/12/012. */public class MyInterpolator implements Interpolator{    private  float mFactor;    private  double mDoubleFactor;    public MyInterpolator() {        mFactor = 0.5f;        mDoubleFactor = 2.0;    }    @Override    public float getInterpolation(float input) {            if (mFactor == 1.0f) {                return input * input;            } else {                Log.i("info", "getInterpolation: 我被调用了");                return (float)Math.pow(input, mDoubleFactor);            }    }}

logi的输出图:

可以的出->getInterPolation()被多次调用,所以Math.pow每调用一次input保存上一次值,一直累加....

速度越来越快.

项目地址:

到这里就差不多了,小伙伴们看懂了吗?