Android - 启动时防止白屏 [英] Android - Prevent white screen at startup

问题描述

众所周知，许多Android应用在第一个活动成为焦点之前，会非常短暂地显示白屏。在以下情况中会出现此问题：

• 扩展全局

  
  

  As we all know, many Android apps display a white screen very briefly before their first Activity comes into focus. This problem is observed in the following cases:

  • Android apps that extend the global Application class and perform major initializations therein. The Application object is always created before the first Activity (a fact that can be observed in the debugger), so this makes sense. This is the cause of the delay in my case.

  • Android apps that display the default preview window before the splash screen.

  Setting android:windowDisablePreview = "true" obviously does not work here. Nor can I set the parent theme of the splash screen to Theme.Holo.NoActionBar as described here, because [unfortunately] my splash screen makes use of an ActionBar.

  Meanwhile, apps that do not extend the Application class do not show the white screen at startup.

  The thing is, ideally the initializations performed in the Application object need to occur before the first Activity is shown. So my question is, how can I perform these initializations on app startup without using an Application object? Possibly using a Thread or Service, I suppose?

  This is an interesting problem to think about. I can't bypass it the usual way (by setting the NoActionBar theme), as tragically my Splash screen actually has an ActionBar due to some unrelated reasons.

  Note:

  I have already referred to the following questions:

  • How To fix white screen on app Start up?

  • Android splash screen is white in the beginning?

  • White screen before splashscreen

  • White background when Android app start up

  • Why there is a white screen appears for 1sec when starting to run the apps in Android?

  References:

  • Patterns – Launch screens.

  • Branded launch screen: the new splash for Android.

  • Splash Screens the Right Way.

  解决方案

  The problem with white background is caused because of android's cold start while the app loads to memory, and it can be avoided with this:

  public class OnboardingWithCenterAnimationActivity extends AppCompatActivity {
  public static final int STARTUP_DELAY = 300;
  public static final int ANIM_ITEM_DURATION = 1000;
  public static final int ITEM_DELAY = 300;
  
  private boolean animationStarted = false;
  
  @Override
  protected void onCreate(@Nullable Bundle savedInstanceState) {
      setTheme(R.style.AppTheme);
      getWindow().getDecorView().setSystemUiVisibility(
              View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_onboarding_center);
  }
  
  @Override
  public void onWindowFocusChanged(boolean hasFocus) {
  
      if (!hasFocus || animationStarted) {
          return;
      }
  
      animate();
  
      super.onWindowFocusChanged(hasFocus);
  }
  
  private void animate() {
      ImageView logoImageView = (ImageView) findViewById(R.id.img_logo);
      ViewGroup container = (ViewGroup) findViewById(R.id.container);
  
      ViewCompat.animate(logoImageView)
          .translationY(-250)
          .setStartDelay(STARTUP_DELAY)
          .setDuration(ANIM_ITEM_DURATION).setInterpolator(
              new DecelerateInterpolator(1.2f)).start();
  
      for (int i = 0; i < container.getChildCount(); i++) {
          View v = container.getChildAt(i);
          ViewPropertyAnimatorCompat viewAnimator;
  
          if (!(v instanceof Button)) {
              viewAnimator = ViewCompat.animate(v)
                      .translationY(50).alpha(1)
                      .setStartDelay((ITEM_DELAY * i) + 500)
                      .setDuration(1000);
          } else {
              viewAnimator = ViewCompat.animate(v)
                      .scaleY(1).scaleX(1)
                      .setStartDelay((ITEM_DELAY * i) + 500)
                      .setDuration(500);
          }
  
          viewAnimator.setInterpolator(new DecelerateInterpolator()).start();
      }
  }
  }
  

  layout

  <?xml version="1.0" encoding="utf-8"?>
  <FrameLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="?colorPrimary"
  android:orientation="vertical"
  >
  
  <LinearLayout
      android:id="@+id/container"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_gravity="center"
      android:gravity="center"
      android:orientation="vertical"
      android:paddingTop="144dp"
      tools:ignore="HardcodedText"
      >
  
      <TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_gravity="center_horizontal"
          android:layout_marginTop="16dp"
          android:alpha="0"
          android:text="Hello world"         android:textAppearance="@style/TextAppearance.AppCompat.Widget.ActionBar.Title.Inverse"
          android:textColor="@android:color/white"
          android:textSize="22sp"
          tools:alpha="1"
          />
  
      <TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_gravity="center_horizontal"
          android:layout_marginTop="8dp"
          android:alpha="0"
          android:gravity="center"
          android:text="This a nice text"
        android:textAppearance="@style/TextAppearance.AppCompat.Widget.ActionBar.Subtitle.Inverse"
          android:textSize="20sp"
          tools:alpha="1"
          />
  
      <Button
          android:id="@+id/btn_choice1"
          android:layout_width="200dp"
          android:layout_height="wrap_content"
          android:layout_marginTop="48dp"
          android:scaleX="0"
          android:scaleY="0"
          android:text="A nice choice"
          android:theme="@style/Button"
          />
  
      <Button
          android:id="@+id/btn_choice2"
          android:layout_width="200dp"
          android:layout_height="wrap_content"
          android:layout_marginTop="4dp"
          android:scaleX="0"
          android:scaleY="0"
          android:text="Far better!"
          android:theme="@style/Button"
          />
  
  </LinearLayout>
  
  <ImageView
      android:id="@+id/img_logo"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_gravity="center"
      android:src="@drawable/img_face"
      tools:visibility="gone"
      />
  </FrameLayout>
  

  img face

  <?xml version="1.0" encoding="utf-8"?>
  <layer-list xmlns:android="http://schemas.android.com/apk/res/android"
          android:opacity="opaque">
  
  <item android:drawable="?colorPrimary"/>
  <item>
      <bitmap
          android:gravity="center"
          android:src="@drawable/img_face"/>
  </item>
  

  Add this theme to your splashscreen in the manifest

  <?xml version="1.0" encoding="utf-8"?>
  <resources>
  <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
      <!-- Customize your theme here. -->
      <item name="colorPrimary">@color/colorPrimary</item>
      <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
      <item name="colorAccent">@color/colorAccent</item>
      <item name="android:windowBackground">@null</item>
  </style>
  
  <style name="AppTheme.CenterAnimation">
      <item name="android:windowBackground">@drawable/ll_face_logo</item>
  </style>
  

  which will produce efect like this

  for more details and more solutions you can check this BlogPost

  这篇关于Android - 启动时防止白屏的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！