在后台使用Intent和call活动

Question

So I'm really confused right now. I have two activities: MainActivity and Main2Activity . I change a value in MainActivity of a textview to "clicked". Then I want to call Main2Activity , change something in there and go back to MainActivity . When I'm going back to MainActivity i want the state to be as I called Main2Activity . How do i get back to the state from MainActivity when I left (=> textview should say "clicked" and not "hello world" as defined in XML)? Here is my code so far: MainActivity:

 package com.plabsproject.testapp;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private Button btn1;
    private TextView textanzeige;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        if (savedInstanceState == null) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            btn1 = (Button) findViewById(R.id.button1);
            btn1.setOnClickListener(btnListener);
            textanzeige = (TextView) findViewById(R.id.helloworld);
            textanzeige.setOnClickListener(btnListener);
            }

        else if (savedInstanceState != null){
            Toast.makeText(this, "Test", Toast.LENGTH_SHORT).show();
        }
        }



        private View.OnClickListener btnListener = new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (view == btn1) {
                    Intent wechselActivity = new Intent(view.getContext(), Main2Activity.class);
                    startActivity(wechselActivity);
                    finish();

                } else if (view == textanzeige) {
                    TextView ändereText = (TextView) findViewById(R.id.helloworld);
                    ändereText.setText("clicked");
                }
            }
        };


}

and Main2Activity:

    package com.plabsproject.testapp;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class Main2Activity extends AppCompatActivity {

    private Button btn1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        btn1 = (Button) findViewById(R.id.Activity2_Button);
        btn1.setOnClickListener(zurück_zur_Activty_1);

    }

    private View.OnClickListener zurück_zur_Activty_1 = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (view == btn1){
                Intent wechselActivity = new Intent(view.getContext(), MainActivity.class);
                wechselActivity.addFlags(Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY);
                startActivity(wechselActivity);
                finish();
            }
        }
    };
}

I think, that this problem is somehow related to the setFlags , but for some reasons, it doesn't work as expected.

Thank you!

Answer 1

Instead of calling startActivity() you can use startActivityForResult() in MainActivity , but don't call finish() in main activity.

Then in Main2Activity set the result by calling setResult() , which will return to the MainActivity .

For more details you can visit the site https://developer.android.com/training/basics/intents/result.html

When you are calling finish() , the activity will remove from memory, so you will not get the previous changes.