为什么我无法通过obtainStyledAttributes从declare styleable TypedArray获取值？

Question

我创建了一个自定义控件，并在attri.xml中定义了一些属性，但是我无法通过obtainStyledAttributes从declare styleable TypedArray获取值，你能帮我查一下我的代码有什么问题吗？

/res/values/attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="TopBar">
        <attr name="title2" format="string" />
        <attr name="titleTextSize2" format="dimension" />
        <attr name="titleTextColor2" format="color" />
        <attr name="leftTextColor" format="color" />
        <attr name="leftBackground" format="color|reference" />
        <attr name="leftText" format="string" />
        <attr name="rightTextColor" format="color" />
        <attr name="rightBackground" format="color|reference" />
        <attr name="rightText" format="string" />
    </declare-styleable>
</resources>

/res/layout/activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:myapp="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.qihoo.foo.TopBar
        android:id="@+id/topbar"
        android:layout_width="match_parent"
        android:layout_height="45dp"
        myapp:leftBackground="@drawable/left"
        myapp:leftText="Back"
        myapp:leftTextColor="#ffffff"

        myapp:rightBackground="@drawable/right"
        myapp:rightText="Move"
        myapp:rightTextColor="#ffffff"

        myapp:title2="title"
        myapp:titleTextColor2="#123412"
        myapp:titleTextSize2="18sp"
        >

    </com.qihoo.foo.TopBar>

</LinearLayout>

/com.foo.samples/TopBar.java

private void init(Context context, AttributeSet attrs, int defStyle) {
        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.Toolbar);

        // I can't get any value from below codes
        mLeftTextColor = ta.getColor(R.styleable.TopBar_leftTextColor, 0);
        mLeftBackground = ta.getDrawable(R.styleable.TopBar_leftBackground);
        mLeftText = ta.getString(R.styleable.TopBar_leftText);

        mRightTextColor = ta.getColor(R.styleable.TopBar_rightTextColor, 0);
        mRightBackground = ta.getDrawable(R.styleable.TopBar_rightBackground);
        mRightText = ta.getString(R.styleable.TopBar_rightText);

        mTitleTextSize = ta.getDimension(R.styleable.TopBar_titleTextSize2, 10);
        mTitleTextColor = ta.getColor(R.styleable.TopBar_titleTextColor2, 0);
        mTitle = ta.getString(R.styleable.TopBar_title2);

        ta.recycle();
    }