如何在Android上集中自定义视图？

Question

I am trying to center the view for different resolutions using the layout, and gravity properties, but it's not working. Is there a way to make the custom view center horizontally across different resolutions?

Do I need to do something on the onMeasure method ?

Here is one of the things I am trying right now, the view is to the left of the center..

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">


    <RelativeLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="50dp"
        android:gravity="center_horizontal">

        <com.application.app.ui.CustomView
            android:id="@+id/ivCoinAnimation"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"/>


    </RelativeLayout>


</FrameLayout>

Answer 1

Assuming you have a View inside a layout like FrameLayout , you would set View 's layout_gravity to center . Don't mix it up with gravity !

Also, it may indeed be necessary to override onMeasure(). Read it's documentation to decide if you need to override it. If you do, be aware that the parameters are encoded with View.MeasureSpec .

Answer 2

You should implement in your custom View class

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)

In it you should calculate height and width for your custom View. If you need to central your custom View in parent layout - make sure that:

• custom View height != parent View height

AND/OR

• custom View width != parent View width

For example:

@Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        final int height = mCircleRadius * 2; //calculated
        final int width = getMeasuredWidth(); //parent width

        setMeasuredDimension(width, height);
    }

Now you can use next for your custom View:

android:layout_centerHorizontal="true"
android:layout_centerVertical="true"

PS You see that android:layout_centerHorizontal="true" gives no effect. The reason is using parent width in onMeasure instead of calculating exact width.

Answer 3

Here is an example how to center two buttons on the screen. This should work with your CustomView, too.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center_vertical">

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal">

        <Button android:text="Button" android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
        <Button android:text="Button" android:id="@+id/button2" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>

    </LinearLayout>
</LinearLayout>