Android principle--Dynamic code layout

Dynamic Code Layout

1. How to add a code layout
2. Problems with code layout considerations
3. Performance comparison of code layout and XML layout

How to add a code layout

For example-- simple layout linearlayout

LinearLayout llayout = new LinearLayout (mcontext);Llayout. SetOrientation(LinearLayout. VERTICAL);LinearLayout. LayoutparamsLayoutparams = new LinearLayout. Layoutparams(LinearLayout. Layoutparams. MATCH_parent, LinearLayout. Layoutparams. MATCH_parent);Llayout. Setlayoutparams(Layoutparams);Button btn = New button (Mcontext);Dt. SetText("This is button");Dt. setpadding(8,8,8,8);Btn. Setlayoutparams(LP);Llayout. AddView(BTN);This is the layout Setcontentview (llayout) set in the activity's OnCreate ();Btn. Setonclicklistener(New View. Onclicklistener() {@Override public void OnClick (View v) {Toast. Maketext(Mcontext,"This is dynamic activity", Toast. LENGTH_long). Show();}        });

Another example-- complex layout relativelayout
Difficulty: Handling the relative position relationship of child controls

Parent control Relativelayout mylayout = new Relativelayout (this);Mylayout. SetBackgroundColor(Color. BLUE); Two child controls Button MyButton = New button (this);EditText myedittext = new EditText (this);Focus: Generate the corresponding ID MyButton. SetId(Generateviewid ());Myedittext. SetId(Generateviewid ());Child control Position Relativelayout. LayoutparamsButtonparams = new Relativelayout. Layoutparams(Relativelayout. Layoutparams. WRAP_content, Relativelayout. Layoutparams. WRAP_content);Buttonparams. AddRule(Relativelayout. CENTER_horizontal);Buttonparams. AddRule(Relativelayout. CENTER_vertical);Relativelayout. LayoutparamsTextparams = new Relativelayout. Layoutparams(Relativelayout. Layoutparams. WRAP_content, Relativelayout. Layoutparams. WRAP_content);Textparams. AddRule(Relativelayout. CENTER_horizontal);Textparams. SetMargins(0,0,0, the);Here's the point Textparams. AddRule(Relativelayout. ABOVE, MyButton. GetId());Add Layout mylayout. AddView(MyButton, Buttonparams);Mylayout. AddView(Myedittext, Textparams);Setcontentview (Mylayout);

The point is that generateViewId() this can be specifically put into the tool class:

    /** * An {@code int} value of May updated atomically. */    Private Static FinalAtomicinteger Snextgeneratedid =NewAtomicinteger (1);/** * Dynamically generated view ID * API level 17 + VIEW.GENERATEVIEWID () generated * API level 17 below need to be generated manually */     Public Static int Generateviewid() {if(Build.VERSION.SDK_INT < Build.version_codes. JELLY_BEAN_MR1) { for(; ; ) {Final intresult = Snextgeneratedid.get ();//aapt-generated IDs has the high byte nonzero, clamp to the range under that.                intNewValue = result +1;if(NewValue >0x00ffffff) NewValue =1;//Roll over to 1, not 0.                if(Snextgeneratedid.compareandset (result, NewValue)) {returnResult }            }        }Else{returnView.generateviewid (); }    }

Problems with code layout considerations

• Control cannot be reused

  First time Add
  Mlinearlayout.addview (Mtextview, mlayoutparams);
  Second time add
  Mlinearlayout.addview (Mtextview, mlayoutparams);
  We have added two times mtextview. This is not allowed, in the parent class layout, there can only be unique objects and cannot be duplicated.

• Whether the Id in different activity will be error

  setId(1)it doesn't work to set the ID directly.
  The build ID must be used View.generateViewId()
  My opinion is to build the static tool class to generate the ID
  Questions about whether the ID int is the same or not, is not currently validated

• Some of the common code

  Textview.settextcolor (0xffff0000);
  Layout.setbackgroundcolor (0x00000000);
  SetOrientation (linearlayout.vertical);
  Setgravity (gravity.center_vertical)
  Setpadding (10, 5, 5, 5);
  SetMargin (8, 0, 0, 0);
  lp.gravity = gravity.center_vertical;
  Lp.topmargin = 5;
  Lp.addrule (relativelayout.center_vertical);
  Lp.addrule (relativelayout.right_of, Id_image_head);

Performance comparison of code layout and XML layout

To test a simple example

Use the code layout as follows:

protected void OnCreate (Bundle savedinstancestate) {Super. OnCreate(savedinstancestate);Mcontext = This;LinearLayout llayout = new LinearLayout (mcontext);Llayout. SetOrientation(LinearLayout. VERTICAL);LinearLayout. LayoutparamsLayoutparams = new LinearLayout. Layoutparams(LinearLayout. Layoutparams. MATCH_parent, LinearLayout. Layoutparams. MATCH_parent);Llayout. Setlayoutparams(Layoutparams);TextView TV = new TextView (mcontext);LinearLayout. LayoutparamsLP = new LinearLayout. Layoutparams(LinearLayout. Layoutparams. MATCH_parent, LinearLayout. Layoutparams. WRAP_content);Lp. SetMargins(8,8,8,8);Tv. Setlayoutparams(LP);Tv. SetText("This is TextView");Tv. setpadding(8,8,8,8);Llayout. AddView(TV);Button btn = New button (Mcontext);Btn. SetText("This is button");Btn. setpadding(8,8,8,8);Btn. Setlayoutparams(LP);Setcontentview (Llayout);}

Three measurements average: (23+28 +)/3 = 23.67ms

Using the same XML layout

<linearlayout  xmlns: Android  = "http://schemas.android.com/apk/res/android"  android:layout_width  =" match_parent " android:layout_height  =" match_parent " android:orientation  =;     <textview  android:text
      = "This is TextView"  android:layout_width  = "match_parent"  android:layout_height  = "wrap_content"  android:layout_margin  =" 8px " android:padding  =" 8px " />     <buttonandroid:layout_width="Match_parent"android:layout_height= "Wrap_content" Android:text="This is button"android:padding="8px"/>                                </linearlayout>

Three measurement averages: (+ + +)/3 = 23.33ms

Conclusion: Although there are few samples, the code layout and the XML layout load time are basically the same and the performance is basically the same.
Insufficient: More complex interface, not tested for the time being.
Idea: Code layout is necessary, if the summary code layout for templates and libraries, the use of generics and reflection, in the interface of reuse and automation, will be more convenient than XML extension.

Android principle--Dynamic code layout