一、通过View实现自定义视图

 

通过构造函数创建可视界面

public class MyView extends View {

  // Constructor required for in-code creation

  public MyView(Context context) {

    super(context);

  }

  // Constructor required for inflation from resource file

  public MyView (Context context, AttributeSet ats, int defaultStyle) {

    super(context, ats, defaultStyle );

  }

  //Constructor required for inflation from resource file

  public MyView (Context context, AttributeSet attrs) {

    super(context, attrs);

  }

通过onDraw()绘制控件。（注意其参数为一个Canvas对象）

@Override

protected void onDraw(Canvas canvas) {

   // Get the size of the control based on the last call to onMeasure.

   int height = getMeasuredHeight();

   int width = getMeasuredWidth();

   // Find the center

   int px = width/2;

   int py = height/2;

   // Create the new paint brushes.

   // NOTE: For efficiency this should be done in

   // the views's constructor

   Paint mTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

   mTextPaint.setColor(Color.WHITE);

   // Define the string.

   String displayText = "Hello World!";

   // Measure the width of the text string.

   float textWidth = mTextPaint.measureText(displayText);

   // Draw the text string in the center of the control.

   canvas.drawText(displayText, px-textWidth/2, py, mTextPaint);

}

通过onMeasure()调整控件大小

  @Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

   int measuredHeight = measureHeight(heightMeasureSpec);

   int measuredWidth = measureWidth(widthMeasureSpec);

  setMeasuredDimension(measuredHeight, measuredWidth);

}

private int measureHeight(int measureSpec) {

   int specMode = MeasureSpec.getMode(measureSpec);

   int specSize = MeasureSpec.getSize(measureSpec);

   //  Default size if no limits are specified.

   int result = 500;

   if (specMode == MeasureSpec.AT_MOST) {

     // Calculate the ideal size of your

     // control within this maximum size.

     // If your control fills the available

     // space return the outer bound.

     result = specSize;

   } else if (specMode == MeasureSpec.EXACTLY) {

     // If your control can fit within these bounds return that value.

     result = specSize;

   }

   return result;

}

处理用户交互事件

使用自定义控件

<com.paad.compass.CompassView/>

二、Adapter简介

Adapter实现了数据绑定到扩展了AdapterView的试图组GroupView.Adapter负责创建被绑定groupView的子视图。

public class MyArrayAdapter extends ArrayAdapter<MyClass> {

  int resource;

  public MyArrayAdapter(Context context,

                         int _resource,

                         List<MyClass> items) {

    super(context, _resource, items);

    resource = _resource;

  }

ArrayAdapter<MyClass>中的MyClass和构造函数的泛型的类型一致。

Context通常是被绑定的对象，_resource是子视图。items是将要用到的泛型数据。

另外一个比较主要的是getView覆盖方法

public View getView(int position, View convertView, ViewGroup parent) {

   LinearLayout todoView;//第n个项的载体

   ToDoItem item = getItem(position);//得到第n个项

   String taskString = item.getTask();

   Date createdDate = item.getCreated();

   SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yy");

   String dateString = sdf.format(createdDate);

   if (convertView == null) {

     todoView = new LinearLayout(getContext());

     String inflater = Context.LAYOUT_INFLATER_SERVICE;

     LayoutInflater li;

     li = (LayoutInflater)getContext().getSystemService(inflater);

     li.inflate(resource, todoView, true);

   } else {

     todoView = (LinearLayout) convertView;

   }

   TextView dateView = (TextView)todoView.findViewById(R.id.rowDate);

   TextView taskView = (TextView)todoView.findViewById(R.id.row);

   dateView.setText(dateString);

   taskView.setText(taskString);

   return todoView;

}

具体的LinearLayout 还有待考证