Question

当屏幕方向更改时，我正在尝试保存和恢复布尔值字段。不管出于什么原因，在第一次方向更改期间，字段都正确地保存/恢复，但是当方向更改回初始状态时，调用onSaveInstanceState()时布尔值是错误的。

根据this answer，我在清单中的相应活动标签上添加了android:configChanges="orientation"。以下代码包含相关方法，为清楚起见对其进行了简化：

public class SignatureActivity extends AppCompactActivity {
    private boolean signaturePadIsEmpty = true;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        String orientation = getResources().getConfiguration().orientation == ORIENTATION_PORTRAIT ? "portrait" : "landscape";
        Log.d(TAG, "onCreate: Orientation is " + orientation + ", signaturePadIsEmpty = " + signaturePadIsEmpty);
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        signaturePadIsEmpty = savedInstanceState.getBoolean("SignaturePadIsEmpty");

        String orientation = getResources().getConfiguration().orientation == ORIENTATION_PORTRAIT ? "portrait" : "landscape";
        Log.d(TAG, "onRestoreInstanceState: Orientation is " + orientation + ", signaturePadIsEmpty = " + signaturePadIsEmpty);
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putBoolean("SignaturePadIsEmpty", signaturePadIsEmpty);

        String orientation = getResources().getConfiguration().orientation == ORIENTATION_PORTRAIT ? "portrait" : "landscape";
        Log.d(TAG, "onSaveInstanceState: Orientation is " + orientation + ", signaturePadIsEmpty = " + signaturePadIsEmpty);
    }
}

这是我开始活动并从纵向->横向然后从横向->纵向更改时的Logcat输出：

06-27 11:50:08.037 32656-32656/com.example.www.debug D/SignatureActivity: onCreate: Orientation is portrait, signaturePadIsEmpty = true
06-27 11:50:12.405 32656-32656/com.example.www.debug D/SignatureActivity: onSaveInstanceState: Orientation is landscape, signaturePadIsEmpty = false
06-27 11:50:12.461 32656-32656/com.example.www.debug D/SignatureActivity: onCreate: Orientation is landscape, signaturePadIsEmpty = true
06-27 11:50:12.465 32656-32656/com.example.www.debug D/SignatureActivity: onRestoreInstanceState: Orientation is landscape, signaturePadIsEmpty = false
06-27 11:50:15.068 32656-32656/com.example.www.debug D/SignatureActivity: onSaveInstanceState: Orientation is portrait, signaturePadIsEmpty = true
06-27 11:50:15.131 32656-32656/com.example.www.debug D/SignatureActivity: onCreate: Orientation is portrait, signaturePadIsEmpty = true
06-27 11:50:15.133 32656-32656/com.example.www.debug D/SignatureActivity: onRestoreInstanceState: Orientation is portrait, signaturePadIsEmpty = true

编辑：该问题原来是由我对签名板的事件处理程序的实现引起的：

private void initializeLayoutElements(final int orientation) {
    signaturePad = findViewById(R.id.signature_pad);
    signaturePad.setOnSignedListener(new SignaturePad.OnSignedListener() {
        @Override
        public void onStartSigning() {
            signaturePadIsEmpty = false;
        }

        @Override
        public void onSigned() {
        }

        @Override
        public void onClear() {
            signaturePadIsEmpty = true;
        }
    });
}

onClear()方法在onRestoreInstanceState()之后被调用，并将标志设置为true。由于@SOreadytohelp发布的解决方案回答了我最初的问题，所以我接受他们的回答。

Answer 1

我在Github上创建了一个简单的演示，以向您展示如何存储和还原实例状态，如果您理解它，请告诉我。这是一个具有按钮的简单应用程序，当您按下按钮时，可以更改布尔值的状态，并且如果旋转屏幕，您仍具有与以前相同的值。我希望这是您要寻找的。

他们的密钥在onRestoreInstanceState()中，得到Boolean；在onSaveInstanceState()中，保存Boolean，而您在{{1 }}

android:configChanges="orientation

实例状态无法正确还原/保存

1 个答案: