android系统开机画面_Android开机画面

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android系统开机画面

Android Splash Screen is the first screen visible to the user when the application’s launched. Splash screen is one of the most vital screens in the application since it’s the user’s first experience with the application.

Android启动画面是启动应用程序时用户可见的第一个屏幕。闪屏是应用程序中最重要的屏幕之一，因为它是用户对应用程序的首次体验。

Splash screens are used to display some animations (typically of the application logo) and illustrations while some data for the next screens are fetched.

启动屏幕用于显示某些动画（通常是应用程序徽标）和插图，同时获取下一个屏幕的一些数据。

Android开机画面 (Android Splash Screen)

Typically, the Activity that has the following intent filter set in the AndroidManifest.xml file is the Splash Activity.

通常，在AndroidManifest.xml文件中设置了以下意图过滤器的Activity是Splash Activity。

<intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>

Android启动画面示例项目结构 (Android Splash Screen Example Project Structure)

There are few ways to create the initial screen i.e. Splash Screen of the application. Let’s see each of them.

有几种创建初始屏幕的方法，即应用程序的启动屏幕。让我们看看它们中的每一个。

闪屏经典方法 (Splash Screen Classical Approach)

SplashActivity.java

package com.journaldev.splashscreen;

import android.content.Intent;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class SplashActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);

        new Handler().postDelayed(new Runnable() {


            @Override
            public void run() {
                // This method will be executed once the timer is over
                Intent i = new Intent(SplashActivity.this, MainActivity.class);
                startActivity(i);
                finish();
            }
        }, 5000);
    }
}

This is how we normally create the layout of our Splash Screen in our application:
activity_splash.xml

通常，这就是我们在应用程序中创建启动画面布局的方式：
activity_splash.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:app="https://schemas.android.com/apk/res-auto"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/black"
    tools:context="com.journaldev.splashscreen.SplashActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="72dp"
        android:layout_height="72dp"
        android:src="@mipmap/ic_launcher"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />


    <ProgressBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:indeterminate="true"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginTop="8dp"
        app:layout_constraintTop_toBottomOf="@id/imageView" />

</android.support.constraint.ConstraintLayout>

Let’s keep the MainActivity.java empty for now.

让我们MainActivity.java保持MainActivity.java空。

The output produced from the above implementation of SplashScreen is given below. We’ve set the theme of the SplashActivity to Theme.AppCompat.NoActionBar in the AndroidManifest.xml file.

下面是上述SplashScreen的实现所产生的输出。我们设置了SplashActivity到Theme.AppCompat.NoActionBar在主题AndroidManifest.xml文件。

Did you see the blank page that came up before the Splash Screen was visible to you?

在启动画面可见之前，您是否看到空白页面？

The above approach isn’t the correct approach. It’ll give rise to cold starts.

上面的方法不是正确的方法。 它会引起冷启动 。

The purpose of a Splash Screen is to quickly display a beautiful screen while the application fetches the relevant content if any (from network calls/database).
With the above approach, there’s an additional overhead that the SplashActivity uses to create its layout.

启动屏幕的目的是在应用程序获取相关内容（从网络调用/数据库）中获取相关内容时，快速显示漂亮的屏幕。
使用上述方法， SplashActivity使用额外的开销来创建其布局。

It’ll give rise to slow starts to the application which is bad for the user experience (wherein a blank black/white screen appears).

它将导致应用程序启动缓慢，这不利于用户体验（其中出现黑屏/白屏）。

带有正确方法的Android启动画面示例 (Android Splash Screen Example with Correct Approach)

The cold start appears since the application takes time to load the layout file of the Splash Activity. So instead of creating the layout, we’ll use the power of the application theme to create our initial layout.

由于应用程序需要时间来加载Splash Activity的布局文件，因此出现冷启动。因此，我们将使用应用程序主题的功能来创建初始布局，而不是创建布局。

Application theme is instantiated before the layout is created. We’ll set a drawable inside the android:windowBackground attribute that’ll comprise of the Activity’s background and an icon using layer-list as shown below.

在创建布局之前，将实例化应用程序主题。我们将在android:windowBackground属性内设置一个drawable，该属性android:windowBackground Activity的背景和使用layer-list的图标组成，如下所示。

splash_background.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="https://schemas.android.com/apk/res/android">

    <item android:drawable="@android:color/black" />
    <item>
        <bitmap
            android:gravity="center"
            android:src="@mipmap/ic_launcher" />
    </item>
</layer-list>

We’ll set the following style as the theme of the activity.

我们将以下样式设置为活动的主题。

styles.xml

<style name="SplashTheme" parent="Theme.AppCompat.NoActionBar">
        <item name="android:windowBackground">@drawable/splash_background</item>
    </style>

The SplashActivity.java file should look like this:

SplashActivity.java文件应如下所示：

package com.journaldev.splashscreen;

import android.content.Intent;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class SplashActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        new Handler().postDelayed(new Runnable() {


            @Override
            public void run() {
                // This method will be executed once the timer is over
                Intent i = new Intent(SplashActivity.this, MainActivity.class);
                startActivity(i);
                finish();
            }
        }, 5000);
    }
}

Note: the theme of the activity is set before anything else. Hence the above approach would give our app a quicker start.

注意：活动的主题设置在其他任何主题之前。因此，以上方法将使我们的应用程序更快速地启动。

Using the theme and removing the layout from the SplashActivity is the correct way to create a splash screen.
This brings an end to android splash screen tutorial. You can download the final Android Splash Screen Project from the link below.

使用主题并从SplashActivity中删除布局是创建初始屏幕的正确方法。
这结束了android启动画面教程。您可以从下面的链接下载最终的Android Splash Screen Project。

Download Android Splash Screen Example Project
下载Android启动画面示例项目