横竖屏或折叠屏切换自动保存和恢复数据

屏幕横竖屏切换或折叠屏切换时，activity会销毁而后重建，后面赋值的变量会为null。 须要onSaveInstanceState保存数据，onCreate 恢复数据。 使用android-state或icepick能使用注解自动保存和恢复，不用每一个变量put 和get。

android-state和icepick

android-state

api 'com.evernote:android-state:1.4.1'
kapt 'com.evernote:android-state-processor:1.4.1'
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BaseActivity

abstract class BaseActivity() : AppCompatActivity(){
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        StateSaver.restoreInstanceState(this, savedInstanceState)
    }
    public override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        StateSaver.saveInstanceState(this, outState)
    }
}
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使用

class TestActivity : BaseActivity() {
    @State
    var username: String? = null
}
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icepick

implementation 'frankiesardo:icepick:3.2.0'
kapt 'frankiesardo:icepick-processor:3.2.0'
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BaseActivity

abstract class BaseActivity() : AppCompatActivity(){
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Icepick.restoreInstanceState(this, savedInstanceState)
    }
    public override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
       Icepick.saveInstanceState(this, outState)
    }
}
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使用

class TestActivity : BaseActivity() {
    @State
    @JvmField
    var username: String? = null
}
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