RelativeLayout位置不匹配

Question

我是Android新手，我想在固定位置绘制3个圆圈。

public class MainActivity extends AppCompatActivity {

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

    final ImageView imgCircle = (ImageView) findViewById(R.id.imgCircle);
    final ImageView imgCircle1 = (ImageView) findViewById(R.id.imgCircle1);
    final ImageView imgCircle2 = (ImageView) findViewById(R.id.imgCircle2);


    //first
    Paint paint = new Paint();
    paint.setColor(Color.BLUE);
    paint.setStyle(Paint.Style.STROKE);
    paint.setStyle(Paint.Style.FILL);
    paint.setAlpha(50);
    Bitmap bmp = Bitmap.createBitmap(300, 300, Bitmap.Config.ARGB_8888);

    Canvas canvas = new Canvas(bmp);
    canvas.drawCircle(bmp.getWidth()/2, bmp.getHeight()/2, 150, paint);
    imgCircle.setImageBitmap(bmp);

（第二个和第三个圆圈的代码与第一个圆圈相同）

XML：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
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="com.example.andav.wisersteps_v2.MainActivity"
android:background="@drawable/foot">

<ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:srcCompat="@mipmap/ic_launcher"
    android:id="@+id/imgCircle2"
    tools:ignore="ContentDescription"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="34dp" />

<ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:srcCompat="@mipmap/ic_launcher"
    android:id="@+id/imgCircle1"

    tools:ignore="ContentDescription"
    android:layout_marginTop="21dp"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/imgCircle2"
    android:layout_toEndOf="@+id/imgCircle2"
    android:layout_marginLeft="18dp"
    android:layout_marginStart="18dp" />

<ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:srcCompat="@mipmap/ic_launcher"

    android:id="@+id/imgCircle"
    tools:ignore="ContentDescription"
    android:layout_marginTop="53dp"
    android:layout_below="@+id/imgCircle1"
    android:layout_alignLeft="@+id/imgCircle1"
    android:layout_alignStart="@+id/imgCircle1" />

</RelativeLayout>

问题是main_activity位置（我想绘制圆圈的位置）与模拟器位置不匹配： before && after

我该如何解决这个问题？