事件

三要素:
  事件源
  事件
  事件监听器

单击事件：
  but.setOnClickListener(new OnClickListener(){
  public void onClick(View v) {
  String str=et.getText().toString();
  tv.setText(str);
  }
  });

按钮选项改变事件：
  rg.setOnCheckedChangeListener(new OnCheckedChangeListener() {
  @Override
  public void onCheckedChanged(RadioGroup group, int checkedId) {
  rb = (RadioButton) findViewById(checkedId);
  String txt = rb.getText().toString();
  tv.setText(txt);
  }
  });

下拉列表选项事件：
  sp.setOnItemSelectedListener(new OnItemSelectedListener() {
  @Override
  public void onItemSelected(AdapterView<?> adapt, View view,int position, long id) {
  TextView tvv = (TextView) view;
  String str = tvv.getText().toString();
  tv.setText(str);
  }
  @Override
  public void onNothingSelected(AdapterView<?> arg0) {
  }
  });

日期和时间事件：
  tp.setOnTimeChangedListener(new OnTimeChangedListener() {
  @Override
  public void onTimeChanged(TimePicker view, int hourOfDay, int minute) {
  tv.setText(hourOfDay+":"+minute);
  }
  });
  dp.init(2017,0, 25, new DatePicker.OnDateChangedListener(){
  @Override
  public void onDateChanged(DatePicker view, int year,int monthOfYear, int dayOfMonth) {
  tv.setText(""+year+monthOfYear+dayOfMonth);
  }
  });

焦点事件：
  et.setOnFocusChangeListener(new OnFocusChangeListener() {
  @Override
  public void onFocusChange(View v, boolean hasFocus) {
  TextView tvv = (TextView)v;
  //hasFocues:是否获得焦点
  if(hasFocus){
  tvv.setText("");
  }else{
  tv.setText(tvv.getText().toString());
  }
  }
  });

长按事件：
  //修改桌面背景需要配置权限
  <uses-permission android:name="android.permission.SET_WALLPAPER" />
  img.setOnLongClickListener(new OnLongClickListener() {
  //两个事件:long--> click
  // false --> 不去运行click
  // true --> 去运行click
  @Override
  public boolean onLongClick(View v) {
  try {
  Day07.this.clearWallpaper();
  Day07.this.setWallpaper(Day07.this.getResources().openRawResource(R.drawable.a));
  tv.setText("设置成功");
  } catch (IOException e) {
  tv.setText("设置失败");
  e.printStackTrace();
  }
  return true;
  }
  });

键盘事件：
et.setOnKeyListener(new OnKeyListener() {
@Override
  public boolean onKey(View v, int keyCode, KeyEvent event) {
  if(event.getAction()==KeyEvent.ACTION_UP){
  String str = et.getText().toString();
  if(str.matches("\w+[@]\w+[.]\w+")){
  iv.setImageResource(R.drawable.a);
  }else{
  iv.setImageResource(R.drawable.icon);
  }
  }
  return false;
  }

  });

触摸事件：
  iv.setOnTouchListener(new OnTouchListener() {
  @Override
  public boolean onTouch(View v, MotionEvent event) {
  tv.setText("("+event.getX()+","+event.getY()+")");
  return false;
  }
  });