android实现对导航Tab设置下划线选中效果

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直接看效果。此linearLayout只有两个Button ,当选中Button1,Button1有个下划线选中效果。当选中Buton2，Button2有个下划线选中效果。

如下图。

package com.daoge.ui;

import roboguice.activity.RoboActivity;
import roboguice.inject.InjectView;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.LinearLayout;

import com.daoge.utils.DensityUtils;
import com.daoge.utils.ResourceReader;
import com.roboguicetest.R;

public class MainActivity extends RoboActivity implements OnClickListener {

    @InjectView(R.id.btnTab001)
    Button btnTab001;
    @InjectView(R.id.btnTab002)
    Button btnTab002;
    @InjectView(R.id.layout_tab)
    LinearLayout layout_tab;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.test_layout);
        initAllViews();
    }

    private void initAllViews() {
        btnTab001.setOnClickListener(this);
        btnTab002.setOnClickListener(this);
    }

    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btnTab001 :
                setTabSelected(btnTab001);
                break;
            case R.id.btnTab002 :
                setTabSelected(btnTab002);
                break;
            default :
                break;
        }
    }

    private void setTabSelected(Button btnSelected) {
        Drawable selectedDrawable = ResourceReader.readDrawable(this, R.drawable.shape_nav_indicator);
        int screenWidth = DensityUtils.getScreenSize(MainActivity.this)[0];
        int right = screenWidth / 2;
        selectedDrawable.setBounds(0, 0, right, DensityUtils.dipTopx(this, 3));
        btnSelected.setSelected(true);
        btnSelected.setCompoundDrawables(null, null, null, selectedDrawable);
        int size = layout_tab.getChildCount();
        for (int i = 0; i < size; i++) {
            if (btnSelected.getId() != layout_tab.getChildAt(i).getId()) {
                layout_tab.getChildAt(i).setSelected(false);
                ((Button) layout_tab.getChildAt(i)).setCompoundDrawables(null, null, null, null);
            }
        }
    }
}

最重要的地方在这里

private void setTabSelected(Button btnSelected) {
        Drawable selectedDrawable = ResourceReader.readDrawable(this, R.drawable.shape_nav_indicator);
        int screenWidth = DensityUtils.getScreenSize(MainActivity.this)[0];
        int right = screenWidth / 2;
        selectedDrawable.setBounds(0, 0, right, DensityUtils.dipTopx(this, 3));
        btnSelected.setSelected(true);
        btnSelected.setCompoundDrawables(null, null, null, selectedDrawable);
        int size = layout_tab.getChildCount();
        for (int i = 0; i < size; i++) {
            if (btnSelected.getId() != layout_tab.getChildAt(i).getId()) {
                layout_tab.getChildAt(i).setSelected(false);
                ((Button) layout_tab.getChildAt(i)).setCompoundDrawables(null, null, null, null);
            }
        }
    }

得到这个Drawable，那么这个Drawable从哪里来呢？？

R.drawable.shape_nav_indicator

看这个drawable.shape文件吧

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <solid android:color="@color/global_red" />

    <size android:width="1000dp" />

    <padding
        android:bottom="2dp"
        android:left="5dp"
        android:right="5dp"
        android:top="2dp" />

</shape>

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