ToggleButton更改了方向更改状态

Question

我有一个CustomButton类(扩展LinearLayout),其中我膨胀包含一个布局ToggleButton(实际上这更复杂,但我在这里简化了问题).

public class CustomButton extends LinearLayout {

    private ToggleButton toggleOnOffButton;

    public CustomButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        LayoutInflater.from(context).inflate(R.layout.custom_button_layout, this);
    }

    @Override
    protected void onFinishInflate() {
        toggleOnOffButton = (ToggleButton) findViewById(R.id.toggle_on_off_button);
        super.onFinishInflate();
    }

    public ToggleButton getToggleOnOffButton() {
        return toggleOnOffButton;
    }
}

custom_button_layout.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content">

    <ToggleButton android:id="@+id/toggle_on_off_button"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:textOff="Off"
                  android:textOn="On"
                  android:layout_alignParentRight="true"
            />
</RelativeLayout>

我有一个活动,我用2 CustomButton-s 夸大布局.第一个toggleButton的开/关状态保存在共享首选项中,我从onCreate方法中加载值.

public class FirstActivity extends Activity
{
    private CustomButton customButton;
    private ToggleButton toggleBut;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        customButton = (CustomButton)findViewById(R.id.toggleButton);
        toggleBut = customButton.getToggleOnOffButton();

        boolean saved = loadPreferences("toggleBut");
        toggleBut.setChecked(saved);
        toggleBut.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                boolean checked = toggleBut.isChecked();
                savePreferences("toggleBut", checked);
            }
        });
    }

    private void savePreferences(String key, boolean value){
        SharedPreferences sharedPreferences = getPreferences(MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putBoolean(key, value);
        editor.commit();
    }

    private boolean loadPreferences(String key){
        SharedPreferences sharedPreferences = getPreferences(MODE_PRIVATE);
        return sharedPreferences.getBoolean(key, true);
    }
}

main.xml中

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"> 
    <com.example.example.cs.ssd.custom.CustomButton
            android:id="@+id/toggleButton"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            />

    <com.example.example.cs.ssd.custom.CustomButton
            android:id="@+id/toggleButton2"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            />
</LinearLayout>

当我启动应用程序时,第一个toggleButton为ON.当我改变屏幕的方向时,自动第一个toggleButton变为Off,甚至saved有值true并被调用toggleBut.setChecked(saved);,我认为这与CutomButton我创建的有关,因为如果main.xml布局只包含1,则CustomButton此问题不会重现.我不确定我做错了什么...这是带有上述代码(作为项目)的存档:存档

Answer 1

如果希望CustomButton在方向更改后保持其当前状态,只需覆盖onSaveInstanceState()和onRestoreInstanceState().

一个办法

我浏览了你的代码并注意到toggleBut在onActivityCreated()之后但在onStart()之前状态正在改变.为了避免让这些方法中的任何一个覆盖切换设置,我只是从onViewCreated()移动这些行:

boolean saved = loadPreferences("toggleBut");
toggleBut.setChecked(saved);

并将它们放在onResume()中.希望有所帮助!

改善方案

当系统尝试恢复默认设置时saveInstanceState,可能会在Fragment.onActivityCreated()中覆盖您的ToggleButton设置.

在CustomButton中,覆盖这些函数,如下所示:

@Override
protected Parcelable onSaveInstanceState() {
    Bundle state = new Bundle();
    state.putParcelable("default", super.onSaveInstanceState());
    state.putParcelable("toggle", toggleOnOffButton.onSaveInstanceState());
    return state;
}

@Override
protected void onRestoreInstanceState(Parcelable state) {
    Bundle bundle = (Bundle) state;
    super.onRestoreInstanceState(bundle.getParcelable("default"));
    toggleOnOffButton.onRestoreInstanceState(bundle.getParcelable("toggle"));
};

了解系统仍然会改变ToggleButton状态,而不需要再做一件事.但是,让我试着解释一下发生的事情:

• onActivityCreated(Bundle savedInstanceState)通过savedInstanceState调用'onRestoreInstanceState(Bundle savedInstanceState)` 将它传递给每个布局元素.
• onRestoreInstanceState()首先从布局的根元素开始,然后遍历布局的层次结构(在这种情况下,它最后设置每个ToggleButton的检查状态).
• 由于默认方法显然不起作用,我们需要为ToggleButtons定义自己的保存/恢复方法.否则,我们在系统调用onRestoreInstanceState()之前所做的任何更改都将由系统再次更改...

因此,最后我们将通过将以下行添加到CustomButton.onFinishInflate()来从此默认行为中排除ToggleButtons:

toggleOnOffButton.setSaveEnabled(false);

瞧,您的CustomButtons会自动保留其状态.