安卓的屬性動畫基本用法（一）
休假歸來，十幾天的婚假過得真快，時間不管對誰都是不夠用的，我們能做的只能是珍惜時間。
上篇文章講解了補間動畫，這次我們來看看屬性動畫，先給大家看看兩張效果圖，大家看看其中的不同：
第一張（補間動畫）：
第二張（屬性動畫）：
模擬器錄製的第二張比較卡，但是大致的效果是能看出來的，大家也能一目瞭然的看出兩張圖的區別吧，那就是點選“飄逸的我”按鈕的點選事件的不同，其實這就是補間動畫和屬性動畫的本質的區別。補間動畫雖能對控制元件做動畫，但並沒有改變控制元件內部的屬性值。而Property Animator則是恰恰相反，Property Animator是通過改變控制元件內部的屬性值來達到動畫效果的。
下面看下程式碼：
以上是MainActivity的所有程式碼，這裡要提的是上篇介紹的補間動畫都是用xml的形式來實現的，而這邊直接程式碼實現，所以像補間動畫的實現大家自己看著用，習慣用程式碼實現的就用程式碼實現，習慣用xml實現的就用xml實現。其實程式碼實現也簡單：public class MainActivity extends Activity implements OnClickListener { private Button btn_move; private Button btn_start; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView(); setListener(); } private void initView() { btn_start = (Button) findViewById(R.id.btn_start); btn_move = (Button) findViewById(R.id.btn_move); } private void setListener() { btn_start.setOnClickListener(this); btn_move.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.btn_start: // viewAnimation(btn_move); //補間動畫 propertyAnimation(btn_move); //屬性動畫 break; case R.id.btn_move: Toast.makeText(this, "點我幹嘛", 0).show(); break; default: break; } } private void propertyAnimation(final View view) { ValueAnimator animator = ValueAnimator.ofInt(0,200); animator.setDuration(1500); animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { int curValue = (int)animation.getAnimatedValue(); view.layout(dp2px(MainActivity.this, 100), dp2px(MainActivity.this, 100)+curValue, dp2px(MainActivity.this, 100)+view.getWidth(), curValue+view.getHeight()+dp2px(MainActivity.this, 100)); } }); //屬性動畫的相關監聽 animator.addListener(new AnimatorListener() { @Override public void onAnimationStart(Animator animation) { // TODO Auto-generated method stub } @Override public void onAnimationRepeat(Animator animation) { // TODO Auto-generated method stub } @Override public void onAnimationEnd(Animator animation) { // TODO Auto-generated method stub } @Override public void onAnimationCancel(Animator animation) { // TODO Auto-generated method stub } }); animator.start(); } private void viewAnimation(View view) { TranslateAnimation translateAnimation = new TranslateAnimation(0, 0, 0, 200); translateAnimation.setFillAfter(true); translateAnimation.setDuration(1500); view.startAnimation(translateAnimation); } /** * 根據手機的解析度從 dp 的單位 轉成為 px(畫素) */ public int dp2px(Context context, int dpValue) { final float scale = context.getResources().getDisplayMetrics().density; return (int) (dpValue * scale + 0.5f); } }
好，下面就來分析屬性動畫怎麼用的吧！private void viewAnimation(View view) { TranslateAnimation translateAnimation = new TranslateAnimation(0, 0, 0, 200); translateAnimation.setFillAfter(true); translateAnimation.setDuration(1500); view.startAnimation(translateAnimation); }
屬性動畫Property Animator包括ValueAnimator和ObjectAnimator；而我們這篇用到的是ValueAnimator。
先看ValueAnimator的相關程式碼：
ValueAnimator animator = ValueAnimator.ofInt(0,200);
animator.setDuration(1500);
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
int curValue = (int)animation.getAnimatedValue();
view.layout(dp2px(MainActivity.this, 100), dp2px(MainActivity.this, 100)+curValue, dp2px(MainActivity.this, 100)+view.getWidth(), curValue+view.getHeight()+dp2px(MainActivity.this, 100));
}
});
animator.start(); ValueAnimator animator = ValueAnimator.ofInt(0,200);
大家可能比較迷惑ofInt(0,200)是啥意思？不用怕，不懂我們就查查原始碼，看看原始碼怎麼說的：
/**
* Constructs and returns a ValueAnimator that animates between int values. A single
* value implies that that value is the one being animated to. However, this is not typically
* useful in a ValueAnimator object because there is no way for the object to determine the
* starting value for the animation (unlike ObjectAnimator, which can derive that value
* from the target object and property being animated). Therefore, there should typically
* be two or more values.
*
* @param values A set of values that the animation will animate between over time.
* @return A ValueAnimator object that is set up to animate between the given values.
*/
public static ValueAnimator ofInt(int... values) {
ValueAnimator anim = new ValueAnimator();
anim.setIntValues(values);
return anim;
}
/**
* Constructs and returns a ValueAnimator that animates between color values. A single
* value implies that that value is the one being animated to. However, this is not typically
* useful in a ValueAnimator object because there is no way for the object to determine the
* starting value for the animation (unlike ObjectAnimator, which can derive that value
* from the target object and property being animated). Therefore, there should typically
* be two or more values.
*
* @param values A set of values that the animation will animate between over time.
* @return A ValueAnimator object that is set up to animate between the given values.
*/
public static ValueAnimator ofArgb(int... values) {
ValueAnimator anim = new ValueAnimator();
anim.setIntValues(values);
anim.setEvaluator(ArgbEvaluator.getInstance());
return anim;
}
/**
* Constructs and returns a ValueAnimator that animates between float values. A single
* value implies that that value is the one being animated to. However, this is not typically
* useful in a ValueAnimator object because there is no way for the object to determine the
* starting value for the animation (unlike ObjectAnimator, which can derive that value
* from the target object and property being animated). Therefore, there should typically
* be two or more values.
*
* @param values A set of values that the animation will animate between over time.
* @return A ValueAnimator object that is set up to animate between the given values.
*/
public static ValueAnimator ofFloat(float... values) {
ValueAnimator anim = new ValueAnimator();
anim.setFloatValues(values);
return anim;
} 這裡我把程式碼改為： ValueAnimator animator = ValueAnimator.ofInt(0,200,-60,300);
其實就是動畫線性點的變化；大家有沒有注意到我在給大家展示原始碼的時候還展示了兩個方法ofArgb(int... values)和ofFloat(float... values)，這兩個方法是什麼意思呢？先不要急，一步步往下看，我們第一步建立了ValueAnimator的例項。
第二部： animator.setDuration(1500); 這個就不解釋了，你懂得！
第三部： animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
int curValue = (int)animation.getAnimatedValue();
view.layout(dp2px(MainActivity.this, 100), dp2px(MainActivity.this, 100)+curValue, dp2px(MainActivity.this, 100)+view.getWidth(), curValue+view.getHeight()+dp2px(MainActivity.this, 100));
}
});
這是最關鍵的一步，動畫時刻更新的監聽器，其中在onAnimationUpdate的重寫方法中有一個 int curValue = (int)animation.getAnimatedValue();可能大家不知道這個得到的int值是什麼，無妨看下日誌：
我只是截取了一部分，其實就是我們設定的ofInt（0,200）值的變化， int curValue = (int)animation.getAnimatedValue(); 其實這邊有一個強制的轉換直接強轉為int了，為什麼？因為我們在建立例項的時候用的是ofInt（），如果你用的是ofFloat（）那這邊只能強制轉換為float。那可能大家有想問什麼時候用ofInt什麼時候用ofFloat呢？其實很簡單具體的就要看你的屬性動畫是用來幹什麼的，我這邊是位置的改變用到的是：
view.layout(dp2px(MainActivity.this, 100), dp2px(MainActivity.this, 100)+curValue, dp2px(MainActivity.this, 100)+view.getWidth(), curValue+view.getHeight()+dp2px(MainActivity.this, 100)); animator.setInterpolator(new BounceInterpolator());
animator.setRepeatCount(1);
animator.setRepeatMode(ValueAnimator.RESTART); 最後送給大家一句話，窮則變，變則通，窮則變通，海闊天空！