如何知道应用何时进入后台

Question

Introduction

Note, the solution provided in the link below did not help me solve my problem:

How to detect when an Android app goes to the background and come back to the foreground

Hallo Stack Overflow Community

I am trying to create simple Android app that allows a user to select text and upper or lower case it, along with a function to remove extra spaces. My app has only three objects, namely two of TButton and one of TMemo . I have encountered a problem with the TMemo and the virtual keyboard. Whenever the virtual keyboard pops up, it displays over the bottom of the TMemo . I have managed to solve this problem by working with the OnVirtualKeyboardHidden and OnVirtualKeybaordShown event handlers of the TForm . Here's how I did it:

procedure TfrmEditor.FormVirtualKeyboardHidden(Sender: TObject;
  KeyboardVisible: Boolean; const Bounds: TRect);
begin
  memInput.Align := memInput.Align.alClient;
end;

procedure TfrmEditor.FormVirtualKeyboardShown(Sender: TObject;
  KeyboardVisible: Boolean; const Bounds: TRect);
begin
  if memInput.Align <> memInput.Align.alTop then
  begin
    memInput.Align := memInput.Align.alTop;
    memInput.Height := memInput.Height - Bounds.Height;
  end;
end;

Problem

So here's my problem: whenever the virtual keyboard is shown and I switch to another app and switch back, the virtual keyboard is hidden but the TMemo TAlignLayout ins't restored back to alClient .

If anyone can help me with this TMemo and virtual keyboard problem I would really appreciate it.

Thank you in advance!

Answer 1

You can use ScrollView in your activity's layout file. By this, you can scroll up and down to view the things hidden by the virtual keybooard.

Here's an example:

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:fillViewport="true">

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:weightSum="1">

            <TextView
                android:layout_width="fill_parent"
                android:layout_height="75dp"
                android:text="Welcome!"
                android:id="@+id/textView"
                android:gravity="center"
                android:textColor="#33b5e5"
                android:textSize="35sp"/>

        </LinearLayout>  
    </LinearLayout>
</ScrollView>

Also, if you you want to "How to know when app goes in backgrond?", you can try adding this function:

public void onPause()
{
    super.oPause();
}

This function is called when app goes in the background. There are more similar functions like onStart(),onResume,onRestart(),onStop() and onDestroy(). They work as their name suggests.