Android application restarts when opened by clicking the application icon

Question

I am new to the Android development world and I've built a simple "Hello World" app. First, activity requests a text. When the "Go" button is clicked, the app launches the second activity displaying the input text.

If I click the HOME button and then click the application icon, the app launches the first activity again but if I press-hold the home button and click the icon from the "Recent apps" bar, it resumes the app where I left.

How do I avoid this?

I need my app to resume even if the launcher icon is clicked.

MainActivity.java,

package com.example.myfirstandroidapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends Activity {
  public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  }

  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
  }
  /** Called when the user clicks the Send button */
  public void sendMessage(View view){
    // Do something in response to button
    Intent intent = new Intent(this, DisplayMessageActivity.class);
    EditText editText = (EditText) findViewById(R.id.txtName);
    String message = editText.getText().toString();
    intent.putExtra(EXTRA_MESSAGE, message);
    startActivity(intent);
  }
}

DisplayActivity.java,

package com.example.myfirstandroidapp;

import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;

public class DisplayMessageActivity extends Activity {

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Get the message from the intent
    Intent intent = getIntent();
    String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

    // Create the text view
    TextView textView = new TextView(this);
    textView.setTextSize(40);
    textView.setText(message);

    // Set the text view as the activity layout
    setContentView(textView);

    // Show the Up button in the action bar.
    setupActionBar();
  }

  /**
   * Set up the {@link android.app.ActionBar}, if the API is available.
   */
  @TargetApi(Build.VERSION_CODES.HONEYCOMB)
  private void setupActionBar() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
      getActionBar().setDisplayHomeAsUpEnabled(true);
    }
  }

  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.display_message, menu);
    return true;
  }

  @Override
  public void onDestroy(){
    super.onDestroy();
  }

  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case android.R.id.home:
      // This ID represents the Home or Up button. In the case of this
      // activity, the Up button is shown. Use NavUtils to allow users
      // to navigate up one level in the application structure. For
      // more details, see the Navigation pattern on Android Design:
      //
      // http://developer.android.com/design/patterns/navigation.html#up-vs-back
      //
      NavUtils.navigateUpFromSameTask(this);
      return true;
    }
    return super.onOptionsItemSelected(item);
  }


}

activity_main.xml,

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingBottom="@dimen/activity_vertical_margin"
        android:paddingLeft="@dimen/activity_horizontal_margin"
        android:paddingRight="@dimen/activity_horizontal_margin"
        android:paddingTop="@dimen/activity_vertical_margin"
        tools:context=".MainActivity" >

        <EditText
            android:id="@+id/txtName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="70dp"
            android:ems="10" >

            <requestFocus />
        </EditText>

        <Button
            android:id="@+id/btnGo"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignBottom="@+id/txtName"
            android:layout_alignParentRight="true"
            android:onClick="sendMessage"
            android:text="Go!" />

        <TextView
            android:id="@+id/textView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignLeft="@+id/txtName"
            android:layout_alignParentTop="true"
            android:layout_marginTop="18dp"
            android:text="Please input your name:"
            android:textAppearance="?android:attr/textAppearanceMedium" />

    </RelativeLayout>

activity_display_message.xml,

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".DisplayMessageActivity" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />



</RelativeLayout>

AndroidManifest.xml,

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myfirstandroidapp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="9"
        android:targetSdkVersion="10" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.myfirstandroidapp.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.example.myfirstandroidapp.DisplayMessageActivity"
            android:label="@string/title_activity_display_message"
            android:parentActivityName="com.example.myfirstandroidapp.MainActivity" >
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.example.myfirstandroidapp.MainActivity" />
        </activity>
    </application>

</manifest>

Answer 1

Issue for me was whenever app in installed by an apk with the click on 'Open' option it used to relaunch every time when we minimize it.

resolved it by

SplashActivity.java:

 override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        if (!isTaskRoot
            && intent.hasCategory(Intent.CATEGORY_LAUNCHER)
            && intent.action != null
            && intent.action.equals(Intent.ACTION_MAIN)) {
            finish()
            return
        }
}

Answer 2

Problem:

I'm not qualified to say this a bug, but there is a behaviour with release builds when starting the application from the launcher. It seems that instead of resuming the previous Activity, it adds a new Activity on top. There is a related bug report on this topic here.

Solution:

I'm working around this this by closing the Launcher Activity if it's not the root of the task, as a result the previous Activity in that task will be resumed.

if (!isTaskRoot()) {
    finish();
    return;
}