Instance of a

Reflection + polymorphism: Generate container instantiation and install view subclasses

Simple implementation steps:

Two methods, one providing the full package name. References to classes and resources (id of XML in Android);

Another approach is to use reflection plus polymorphic loading;

	private List<View> getViewList(List<View> list){
		if(list == null)
			list = new ArrayList<View>();
		String vName[] = {"com.sansui.Memo.MemoView",
					"com.sansui.Calendar.CalendarView","com.sansui.ClassRoom.ClassRoom"};
		int vNo[] = {R.layout.memoview, R.layout.calendarview , R.layout.classroomview};
		for(int i = 0 ; i < vNo.length ; i++)
			list.add(getInstanceView(vName[i],vNo[i]));
		return list; 
	}
 
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The three classes loaded with vNames are classes for custom controls. The topmost parent class is View(similar to J2SE object).

	private View getInstanceView(String className,int resouces){
		XmlPullParser parser = this.getResources().getXml(resouces);
		AttributeSet attributes = Xml.asAttributeSet(parser);
		Object view = null;
		try {
			Class clazz = Class.forName(className);
			Constructor con = clazz.getDeclaredConstructor(Context.class,AttributeSet.class);
			view = con.newInstance(MainView.this,attributes);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		} 		
		return (View)view;
	}	
 
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The class is loaded with a simple reflection (that is, the matching and instantiation of the concrete class and XML), and then loaded into the List container

It’s setting the viewPager, that’s what this was written for; Do you find it convenient? If you have multiple views, it’s easy and flexible to load, and this method is quite reusable;

Example 2

Gets the control object by reflection

	@ViewInject(R.id.pull_to_refresh_listview)
	private PullToRefreshListView pullToRefreshListView;
 
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No more code initializationCopy the code

pullToRefreshListView = (PullToRefreshListView) findViewById(R.id.pullToRefreshListView);

Implementation (there is a lot of code on the web) : one interface and one class

interface

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
 
 
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface ViewInject {
    int value();
}
 
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class

import android.app.Activity; import java.lang.reflect.Field; @SuppressWarnings("unused") public class ViewInjectClass { public static void autoInjectAllField(Activity activity) { Clazz = activity.getClass(); Field[] fields = clazz.getDeclaredFields(); Field[] fields = clazz.getDeclaredFields(); try { for (Field field : Fields) {/ / whether fields marked InjectView if (field. IsAnnotationPresent (ViewInject. Class)) {/ / if the labeling, Get its ID ViewInject Inject = field.getannotation (viewinject.class); int id = inject.value(); If (id > 0) {// Reflect access to private member, must add this line field.setaccessible (true); Try {// Then copy field.set(activity, activity.findViewById(id)) for this property; } catch (Exception ex) { } } } } } catch (Exception ex) { ex.printStackTrace(); }}}Copy the code

Usage and suggestions: Unified write a BaseActivityCopy the code

import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import com.anykaalibrary.ViewInjectClass; public class BaseActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); } @Override public void setContentView(int layoutResID) { super.setContentView(layoutResID); ViewInjectClass.autoInjectAllField(this); } } public class MainActivity extends BaseActivity { @ViewInject(R.id.pull_to_refresh_listview) private PullToRefreshListView pullToRefreshListView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); }}Copy the code

I don’t actually recommend this, but I would like to see development tools that can use code like this, Automatically change the code to before compilation pullToRefreshListView = (pullToRefreshListView) the findViewById (R.i d.p ullToRefreshListView); In this form.