Question

我有一个自定义视图，让我们说这是它的代码：

public class CustomView extends View {

    boolean visible;
    boolean enabled;

    public CustomView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);

        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomView, 0, 0);
        try {
            visible = a.getBoolean(R.styleable.CustomView_visible, true);
            enabled = a.getBoolean(R.styleable.CustomView_enabled, true);
        } finally {
            a.recycle();
        }

        // Apply XML attributes here
    }

    @Override
    public Parcelable onSaveInstanceState() {
        // Save instance state
        Bundle bundle = new Bundle();
        bundle.putParcelable("superState", super.onSaveInstanceState());
        bundle.putBoolean("visible", visible);
        bundle.putBoolean("enabled", enabled);

        return bundle;
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        // Restore instance state
        // This is called after constructor
        if (state instanceof Bundle) {
            Bundle bundle = (Bundle) state;
            visible = bundle.getBoolean("visible");
            enabled = bundle.getBoolean("enabled");

            state = bundle.getParcelable("superState");
        }
        super.onRestoreInstanceState(state);
    }
}

非常简单。我的自定义视图从XML读取属性并应用它们。这些属性在配置更改时保存和恢复。

但如果我有两种不同的布局，例如两种不同的方向：

[layout-port/view.xml]
<CustomView
    custom:visible="true"
    custom:enabled="true"

[layout-land/view.xml]
<CustomView
    custom:visible="false"
    custom:enabled="false"

我的问题是，在更改设备方向时，视图状态会保存为可见并启用，但现在XML布局表明视图不应该具有。在onRestoreInstanceState之前调用构造函数，并且XML属性将被保存的状态覆盖。我不希望这样，XML优先于保存状态。

我做错了什么？解决这个问题的最佳方法是什么？

Answer 1

在您的情况下，您必须将当前方向存储在Parcelable中以及其他属性，并且仅在恢复方向等于当前方向的情况下应用这些已恢复的属性（即，活动已被OS销毁和恢复）。在您的情况下，我会使用android:tag来定义当前的方向，如下所示：

[layout-port/view.xml]
<CustomView
    android:tag="port"
    custom:visible="true"
    custom:enabled="true"

[layout-land/view.xml]
<CustomView
    android:tag="land"
    custom:visible="false"
    custom:enabled="false"

然后你的自定义视图类就像：

public class ScheduleView extends View {

    String orientation;
    boolean visible;
    boolean enabled;

    public ScheduleView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);

        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomView, 0, 0);
        try {
            visible = a.getBoolean(R.styleable.CustomView_visible, true);
            enabled = a.getBoolean(R.styleable.CustomView_enabled, true);
        } finally {
            a.recycle();
        }

        orientation = (String) getTag();
    }

    @Override
    public Parcelable onSaveInstanceState() {
        // Save instance state
        Bundle bundle = new Bundle();
        bundle.putParcelable("superState", super.onSaveInstanceState());
        bundle.putBoolean("visible", visible);
        bundle.putBoolean("enabled", enabled);
        bundle.putString("orientation", orientation);

        return bundle;
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        // Restore instance state
        // This is called after constructor
        if (state instanceof Bundle) {
            Bundle bundle = (Bundle) state;

            String restoredOrientation = bundle.getString("orientation");
            if (restoredOrientation.equals(orientation)) {
                visible = bundle.getBoolean("visible");
                enabled = bundle.getBoolean("enabled");
            }

            state = bundle.getParcelable("superState");
        }
        super.onRestoreInstanceState(state);
    }
}

没有正确测试，但它应该工作。希望它会有所帮助。

Answer 2

基本上，您需要将状态分为纵向和横向，这意味着您还必须保存特定的配置状态。

final boolean isPortrait = 
            getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT;
bundle.putBoolean("isPortrait", isPortrait);

然后恢复状态时：

final boolean savedOrientation = bundle.getBoolean("isPortrait");
final boolean currentOrientation = 
            getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT;

if (savedOrientation == currentOrientation) {
    // now retrieve saved values
} else {
    // do nothing, values are initialized in constructor
}

在应用XML属性之前恢复视图状态

2 个答案: