APP启动页背景颜色变化

在APP的启动页经常会有一些渐变效果。

如果是从半透明渐变为不透明，用View动画AlphaAnimation就能完成。

而View动画只有渐变，旋转，平移，和缩放四种动画效果，是完成不了颜色变化的任务的。所以需要用到属性动画。

demo下载：http://download.csdn.net/download/qq_25806863/9934747

下面是三种用属性动画让启动页背景颜色渐变的方法：

界面准备

几个启动页面都用同一套布局，很简单

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/launch"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:gravity="center"    android:orientation="vertical">    <ImageView        android:layout_width="50dp"        android:layout_height="50dp"        android:layout_gravity="center_horizontal|bottom"        android:src="@mipmap/ic_launcher" />    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center"        android:layout_marginTop="20dp"        android:gravity="center"        android:text="V5.1" /></LinearLayout>

1.ValueAnimator.ofArgb,由红变白

ValueAnimator动画改变的是数值，不会直接改变属性，所以需要在监听数值变化的时候自己去设置属性。

public class Launch1Activity extends AppCompatActivity {    private LinearLayout launch;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_launch1);        launch = (LinearLayout) findViewById(R.id.launch);        startAnimate();    }    private void startAnimate() {        ValueAnimator valueAnimator = ValueAnimator.ofArgb(Color.RED, Color.WHITE);        valueAnimator.setDuration(3000);        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {            @Override            public void onAnimationUpdate(ValueAnimator valueAnimator) {              //这里设置背景颜色                launch.setBackgroundColor((Integer) valueAnimator.getAnimatedValue());            }        });        valueAnimator.addListener(new AnimatorListenerAdapter() {            @Override            public void onAnimationEnd(Animator animation) {                super.onAnimationEnd(animation);              //跳转到首页                skip();            }        });        valueAnimator.start();    }    private void skip() {        startActivity(new Intent(this, MainActivity.class));        finish();    }}

2.ObjectAnimator.ofObject由红变蓝

这里用到了ColorDrawable来作为背景。

通过改变ColorDrawable的颜色来达到效果。

public class Launch2Activity extends AppCompatActivity {    private LinearLayout launch;    private ColorDrawable background;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_launch1);        launch = (LinearLayout) findViewById(R.id.launch);        background = new ColorDrawable(Color.RED);        launch.setBackground(background);        startAnimate();    }    private void startAnimate() {        ArgbEvaluator evaluator = new ArgbEvaluator();        ObjectAnimator objectAnimator = ObjectAnimator.ofObject(this, property, evaluator, Color.BLUE);        objectAnimator.setDuration(3000);        objectAnimator.addListener(new AnimatorListenerAdapter() {            @Override            public void onAnimationEnd(Animator animation) {                super.onAnimationEnd(animation);                skip();            }        });        objectAnimator.start();    }    private void skip() {        startActivity(new Intent(this, MainActivity.class));        finish();    }    private  Property<Launch2Activity, Object> property = new Property<Launch2Activity, Object>(Object.class, "background") {        @Override        public void set(Launch2Activity object, Object value) {            object.background.setColor((Integer) value);        }        @Override        public Object get(Launch2Activity object) {            return object.background.getColor();        }    };}

3.ObjectAnimator.ofInt由红变黄

这个就是简单的属性动画了。

public class Launch3Activity extends AppCompatActivity {    private LinearLayout launch;    private ColorDrawable background;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_launch1);        launch = (LinearLayout) findViewById(R.id.launch);        startAnimate();    }    private void startAnimate() {        ArgbEvaluator evaluator = new ArgbEvaluator();        ObjectAnimator objectAnimator = ObjectAnimator.ofInt(launch, "backgroundColor", Color.RED, Color.YELLOW);        objectAnimator.setEvaluator(new ArgbEvaluator());        objectAnimator.setDuration(3000);        objectAnimator.addListener(new AnimatorListenerAdapter() {            @Override            public void onAnimationEnd(Animator animation) {                super.onAnimationEnd(animation);                skip();            }        });        objectAnimator.start();    }    private void skip() {        startActivity(new Intent(this, MainActivity.class));        finish();    }}

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