Android principle-dynamic code layout and android principle Layout

Android principle-dynamic code layout and android principle Layout
Dynamic code layout how to add code Layout

For example --Simple LinearLayout

LinearLayout llayout = new LinearLayout (mContext); llayout. setOrientation (LinearLayout. VERTICAL); LinearLayout. layoutParams layoutParams = new LinearLayout. layoutParams (LinearLayout. layoutParams. MATCH_PARENT, LinearLayout. layoutParams. MATCH_PARENT); llayout. setLayoutParams (layoutParams); Button btn = new Button (mContext); btn. setText ("This is Button"); btn. setPadding (8, 8, 8, 8); btn. setLayoutParams (lp); llayout. addView (btn); // This is to set the layout setContentView (llayout) in onCreate () of the Activity; 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 positional 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); // key: generate the corresponding ID myButton. setId (generateViewId (); myEditText. setId (generateViewId (); // the position of the child control, RelativeLayout. layoutParams buttonParams = new RelativeLayout. layoutParams (RelativeLayout. layoutParams. WRAP_CONTENT, RelativeLayout. layoutParams. WRAP_CONTENT); buttonParams. addRule (RelativeLayout. CENTER_HORIZONTAL); buttonParams. addRule (RelativeLayout. CENTER_VERTICAL); RelativeLayout. layoutParams textParams = new RelativeLayout. layoutParams (RelativeLayout. layoutParams. WRAP_CONTENT, RelativeLayout. layoutParams. WRAP_CONTENT); textParams. addRule (RelativeLayout. CENTER_HORIZONTAL); textParams. setMargins (0, 0, 0, 80); // focus on textParams. addRule (RelativeLayout. ABOVE, myButton. getId (); // Add the layout myLayout. addView (myButton, buttonParams); myLayout. addView (myEditText, textParams); setContentView (myLayout );

The key point isgenerateViewId(), Which can be specifically put into the tool class:

/*** An {@ code int} value that may be updated atomically. */private static final AtomicInteger sNextGeneratedId = new AtomicInteger (1);/*** dynamically generate View ID * api level 17 or above. generateViewId () to generate * api level 17 or lower, you need to manually generate */public static int generateViewId () {if (Build. VERSION. SDK_INT <Build. VERSION_CODES.JELLY_BEAN_MR1) {for (;) {final int result = sNextGeneratedId. get (); // aapt-generated IDs have the high byte nonzero; clamp to the range under that. int newValue = result + 1; if (newValue> 0x00FFFFFF) newValue = 1; // Roll over to 1, not 0. if (sNextGeneratedId. compareAndSet (result, newValue) {return result ;}} else {return View. generateViewId ();}}

Code layout considerations

• Controls cannot be reused

  // Add for the first time
  MLinearLayout. addView (mTextView, mLayoutParams );
  // Add for the second time
  MLinearLayout. addView (mTextView, mLayoutParams );
  // We added the mTextView twice. This is not allowed. In the parent class layout, there can only be unique objects and cannot be repeated.

• Whether the IDs of different activities are the same

  Set ID directlysetId(1)No.
  ID generation must useView.generateViewId()
  My opinion is to create a static tool class to generate an ID
  Whether an error occurs when the int value of the ID is the same.

• Some 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 Between code layout and XML Layout

Test a simple example

The Code layout is as follows:

    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        mContext = this;        LinearLayout llayout = new LinearLayout(mContext);        llayout.setOrientation(LinearLayout.VERTICAL);        LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(                LinearLayout.LayoutParams.MATCH_PARENT,                LinearLayout.LayoutParams.MATCH_PARENT        );        llayout.setLayoutParams(layoutParams);        TextView tv = new TextView(mContext);        LinearLayout.LayoutParams lp = 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);    }

Mean of three measurements: (23 + 28 + 20)/3 = 23.67 ms

Use 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="vertical">    <TextView        android:text="This is TextView"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_margin="8px"        android:padding="8px"/>    <Button        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="This is Button"        android:padding="8px"/></LinearLayout>

Mean of three measurements: (20 + 26 + 24)/3 = 23.33 ms

Conclusion: although the sample size is single and the number of samples is small, the Code layout and XML layout have the same loading time and performance.
Insufficient: more complex interface, not tested yet.
Idea: Code layout is necessary. If you summarize the code layout as a template and a library and use generics and reflection to reuse and automate the interface, it will be easier to expand than XML.