Android未还原实例状态

Question

I know similar questions have been asked but none of the solutions to those questions have been working for me.

When I go ahead and try to save the state of my app, the state of the EditText views are not being saved and restored. I went ahead and commented everything out and just put in a temporary string to save but when the app loads up again, the onCreate() method does not print 'Restoring instance state'

package com.fwumdesoft.udppacketsender;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

/**
 * Posts a UDP message with the given data to the
 * target address on the target port.
 */
class UdpPostActivity extends AppCompatActivity {
    private static final String TAG = "UdpPostActivity";

    private static final String stateTextTargetHost = "com.fwumdesoft#TargetHost";
    private static final String stateTextTargetPort = "com.fwumdesoft#TargetPort";
    private static final String stateTextHexData = "com.fwumdesoft#HexData";
    private static final String stateTextStringData = "com.fwumdesoft#StringData";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.v(TAG, "onCreate");
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_udp_post);

        if (savedInstanceState != null) {
//            ((EditText) findViewById(R.id.txtAddress)).setText(savedInstanceState.getString(stateTextTargetHost));
//            ((EditText) findViewById(R.id.txtPort)).setText(savedInstanceState.getString(stateTextTargetPort));
//            ((EditText) findViewById(R.id.txtData)).setText(savedInstanceState.getString(stateTextHexData));
//            ((EditText) findViewById(R.id.txtStringData)).setText(savedInstanceState.getString(stateTextStringData));
            String text = savedInstanceState.getString(stateTextStringData);
            Log.v(TAG, "Restoring instance state");
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
//        outState.putString(stateTextTargetHost, ((EditText)findViewById(R.id.txtAddress)).getText().toString());
//        outState.putString(stateTextTargetPort, ((EditText)findViewById(R.id.txtPort)).getText().toString());
//        outState.putString(stateTextHexData, ((EditText)findViewById(R.id.txtData)).getText().toString());
//        outState.putString(stateTextStringData, ((EditText)findViewById(R.id.txtStringData)).getText().toString());
        super.onSaveInstanceState(outState);
        outState.putString(stateTextStringData, "test");
        Log.v(TAG, "Saved instance state");
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        Log.v(TAG, "onRestore");
//        ((EditText)findViewById(R.id.txtAddress)).setText(savedInstanceState.getString(stateTextTargetHost));
//        ((EditText)findViewById(R.id.txtPort)).setText(savedInstanceState.getString(stateTextTargetPort));
//        ((EditText)findViewById(R.id.txtData)).setText(savedInstanceState.getString(stateTextHexData));
//        ((EditText)findViewById(R.id.txtStringData)).setText(savedInstanceState.getString(stateTextStringData));

    }

In the logcat output I get "Saved instance state" and then "onCreate" but I do not get "Restoring instance state" or "onRestore" when restarting the app.

Answer 1

You should refer to the key you gave in outState when checking if savedInstanceState is not null, like this.

            if (savedInstanceState != null) {
            String text = savedInstanceState.getString("test");
            Log.v(TAG, "Restoring instance state");
        }

This documentation may shed some light

https://developer.android.com/guide/components/activities/activity-lifecycle.html

Answer 2

Go to debug mode and see if your onCreate is being called. Do you have android:configChanges set in your manifest?