如何为我的相对布局设置alpha值？

Question

嗨,我正在尝试为我的相对布局设置alpha值但是,我得到错误如何解决这个帮助我.....

我在我的xml布局中有三个布局第一个布局用于背景第二个布局用于标题第三个布局用于页脚.我希望设置alpha值2和第3布局,所以我尝试了很多方法仍然我不知道请告诉如何设置alpha值

xml代码:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="fill_parent"
    android:layout_alignParentLeft="true"
    android:orientation="vertical" 
    android:background="@drawable/blue">

    <RelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="60px"
        android:orientation="horizontal"
        android:layout_alignParentTop="true"
        android:background="@drawable/gradient_black"
        android:id="@+id/ttest">
       <ImageView
            android:id="@+id/imageView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"

        />

        <TextView
            android:id="@+id/header_text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_marginLeft="6dp"
            android:layout_toRightOf="@+id/imageView1"
            android:text="settings"
            android:textColor="@color/white"
            android:textSize="20sp" />

    </RelativeLayout>

    <RelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="55px"

        android:background="@drawable/gradient_black"
        android:gravity="bottom"
        android:orientation="horizontal"
        android:layout_alignParentBottom="true" >
  <ImageView
            android:id="@+id/imageView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="ssss"
        />  

    </RelativeLayout>

</RelativeLayout>

码:

public class DesignActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        int width = getWindowManager().getDefaultDisplay().getWidth();
        int height = getWindowManager().getDefaultDisplay().getHeight();


        ImageView imgHead = (ImageView)findViewById(R.id.imageView1);

        ImageView imgbottom = (ImageView)findViewById(R.id.imageView2);


        imgbottom.setImageResource(R.drawable.back);
        imgbottom.setLayoutParams(new RelativeLayout.LayoutParams(width/8, height/8));


        imgHead.setImageResource(R.drawable.b);
        imgHead.setLayoutParams(new RelativeLayout.LayoutParams(width/8, height/8));
     //   RelativeLayout relative = (RelativeLayout)findViewById(R.id.ttest);

    }
}

Answer 1

试试这个

AlphaAnimation alpha = new AlphaAnimation(0.5F, 0.5F);
alpha.setDuration(0); // Make animation instant
alpha.setFillAfter(true); // Tell it to persist after the animation ends
// And then on your layout
yourLayout.startAnimation(alpha);

Answer 2

RelativeLayout rl; ...
rl.setAlpha(0.5F);

<RelativeLayout
    android:id="@+id/rl"
    android:layout_width="200dp"
    android:layout_height="200dp"
    android:background="@drawable/bg"
    android:alpha="0.5">