ImageView can't be clicked like a button

• Everything is OK except the onClick() method.It didn't work at all.When I click the any of the 3 images,nothing happened.


• I know that I can solve the problem by using Button or ImageButton.But where is the bug in my code?


• 
  

  Here is a part of my code:

  
  

  
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      //......
      discover = (ImageView) findViewById(R.id.discover);
      to_new = (ImageView) findViewById(R.id.to_new);
      me = (ImageView) findViewById(R.id.me);
  }
  
  @Override
  public void onClick(View v) {
      switch(v.getId()){
      case R.id.discover:
          discover.setImageResource(R.drawable.discover_2);
          to_new.setImageResource(R.drawable.to_new);
          me.setImageResource(R.drawable.me);
          break;
      case R.id.to_new:
          discover.setImageResource(R.drawable.discover);
          to_new.setImageResource(R.drawable.to_new_2);
          me.setImageResource(R.drawable.me);
          break;
      case R.id.me:
          discover.setImageResource(R.drawable.discover);
          to_new.setImageResource(R.drawable.to_new);
          me.setImageResource(R.drawable.me_2);
          break;
      }
  }
  
  

XML:

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <ImageView
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="60dp"
            android:src="@drawable/blank"/>
        <ImageView
            android:id="@+id/discover"
            android:layout_width="60dp"
            android:layout_height="60dp"
            android:src="@drawable/discover"
            android:clickable="true"/>
        <ImageView
            android:id="@+id/to_new"
            android:layout_width="60dp"
            android:layout_height="60dp"
            android:layout_gravity="center"
            android:src="@drawable/to_new"
            android:clickable="true"/>
        <ImageView
            android:id="@+id/me"
            android:layout_width="60dp"
            android:layout_height="60dp"
            android:src="@drawable/me"
            android:clickable="true"/>
    </LinearLayout>