老生常谈的问题，直接设置android:windowBackground全屏的图片,太消耗内存，这里使用layer-list设置全全屏的背景图，直接上代码

给activity设置android:theme="@style/welcome"(相较于给Application设置，给activity设置更合理，)

        <!--主界面-->
        <activity
            android:name=".activity.MainActivity"
            android:configChanges="orientation|keyboardHidden|screenSize"
            android:exported="true"
            android:launchMode="singleTask"
            android:label="@string/app_name"
            android:theme="@style/welcome"
            android:screenOrientation="sensorLandscape">
        </activity>

定义style

    <style name="welcome" parent="AppTheme">

        <item name="android:windowBackground">@drawable/welcome_layer_list</item>

    </style>

定义layer-list

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

这样就成功了

**最后别忘了设置 getWindow().setBackgroundDrawable(null); **

public abstract class AbsBaseActivity extends AppCompatActivity {

    public Context context;
    public Unbinder unbinder;
    //是否是当前activity
    public boolean isCurrentActivity;

    @Override
    @DebugLog
    protected void onCreate(@Nullable Bundle savedInstanceState) {

        getWindow().setBackgroundDrawable(null);
        super.onCreate(savedInstanceState);

        context = this;
        isCurrentActivity = true;

        setContentView();
        //添加Activity到堆栈
        AppManager.getAppManager().addActivity(this);
        //绑定view
        bindKnife();
//        bindButterKnife();
        viewInit();
        dataInit();
        eventInit();
    }
}