The ultimate solution to the problem of a brief black or white screen when entering the startup page

irontec has launched an open source project PHP for Android (PFA) to bring PHP to the Android platform. Now let's introduce it.

Problem Description

In Android project development, when we start the app, the screen will appear white for a period of time Or the screen goes black, and the length of time varies on different devices. It greatly affects the user experience, so it is necessary for us to optimize it.

Cause of black and white screen problem

When we start an APP, if the Application to which the app belongs is not running in the background, the system will first create a new process to run the APP, but the creation and initialization of the process take time. Before this action is completed, if the initialization time is too long, there may be no movement on the screen, and the user will think that the APP has not been clicked and click again. application icon, which greatly reduces the user experience, so Android needs to make timely feedback to respond to the user's click to start the action. This leads to the emergence of StartingWindow (also called PreviewWindow's preview window), which looks like The App has been started, but the data content has not been initialized yet.

StartingWindow generally appears before the application process is created and initialized successfully. The purpose is to tell the user that the system has received the operation and is responding. After the program initialization is completed, the startup page UI is drawn and the window will be removed at the same time. , so he is just a temporary window.

Generally, we will set the Theme for Application and Activity, and the system will initialize the StartingWindow according to the set Theme. The top level of the Window layout is DecorView. StartingWindow displays an empty DecorView, but the background color set in the Theme specified by the Activity will be applied to the DecorView. If the Activity does not specify a Theme, the Application's Theme will be used (the Application system requires that the Theme be set). Our settings in Style determine whether the white screen or black screen is displayed, as follows:

<application        // ....
        android:theme="@style/AppTheme">

If our AppTheme uses the Light theme as defined below, the display will be a white screen, otherwise if we use Black theme, then the display will be a black screen:

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">

Solution

1. First, create a new layer-list under res/drawable, with a random name, such as splash.xml : Reference for writing
layer-list: https://www.jb51.net/article/130850.htm

<?xml version="1.0" encoding="utf-8"?><layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- 背景颜色 -->
    <item android:drawable="@color/white" />

    <item>
        <!-- 图片 -->
        <bitmap            android:gravity="center"
            android:src="@drawable/wel_page" />
    </item></layer-list>

layer-list Everyone can write it, the top is the background color, and the bottom is a picture Picture, this picture can be a full-screen picture or a small picture. If it is a full-screen image, the color above does not need to be set. If it is a small image, you need to specify the color and the location of the image.

2. Set the Window background for the theme: You can use our layer-list above as the background, and of course you can also set a full-screen image.

<style name="SplashTheme" parent="AppBaseTheme">
    <!-- 欢迎页背景引用刚才写好的 -->
    <item name="android:windowBackground">@drawable/splash</item>
    <item name="android:windowFullscreen">true</item>
    <!-- <item name="android:windowIsTranslucent">true</item> --> <!-- 透明背景不要了 --></style>

3. Define the theme of SplashActivity as SplashTheme in AndroidManifest.xml: Note here that the theme used by application is AppTheme, and the theme used by SplashActivity is SplashTheme. The effect of this is that as long as SplashActivity uses the StartAppTheme theme, other activities use the AppTheme theme.

<activity android:name=".SplashActivity"
    android:theme="@style/SplashTheme">
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>
            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter></activity>

4. To implement SplashActivity, just start your MainActivity directly in onCreate(), without setContentView():

public class SplashActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        // setContentView(R.layout.activity_load_sir);
        new Handler().postDelayed(new Runnable() {            @Override
            public void run() {
                Intent intent = new Intent(SplashActivity.this,MainActivity.class);
                startActivity(intent);
                finish();
            }
        }, 3000);
    }
}

Extension

In the second step above It is mentioned in the article that you can set the background to a picture directly without using layer-list, but it is not recommended to directly use a .png picture as the background because the screen size is too large and the picture display will be deformed. If possible, we can also use it. 9. png background image to achieve, but there is a flaw in the way of using images is that the splash image is written in the theme, the memory of the image cannot be released, and using layer-list saves memory.

Related recommendations:

PHP for Android project

Android Animation_html/css_WEB-ITnose

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