Spinner is actually a list selection box, but Android's list selection box does not need to display a drop-down list, but is equivalent to popping up a menu for the user to choose.
Both Spinner and Gallery inherited AbsSpinner. AbsSpinner inherited AdapterView, so he also showed the characteristics of AdapterView: Just provide AdapterView Adapter.
The android:entries attribute is not defined by Spinner and is not defined in AbsSpinner, so Gallery (inheriting AbsSpinner) also supports this XML attribute.
If the developer can use Spinner to determine the list items in the list selection box, then there is no need to write code. Simply specify the android:entries attribute for Spinner to make Spinner work normally; if the program needs to dynamically determine Spinner's List items, or programs that need to customize Spinner's list items, can use Adapter to provide list items.
Two Spinner components are defined in the following interface layout file. One of the Spinner components specifies the android:entries attribute, so you need to set the adapter for him in the Activity.
Spinner Style EncyclopediaThere are many special styles and even exaggerated styles for the spinner controls. Here we just experiment with various spinner style effects by changing the system's own xml style.
First create the simplest spinner in your project:
There are two places that need to be replaced:
ArrayAdapter String adapter =
New ArrayAdapter "String"( this,
android.R.layout.simple_spinner_item);
The second parameter here is the android.R system's own xml style, we will see the spinner's intuitive style is as follows:
First, set the data source
Second, binding data source
Third, set the selected event
I. Introduction
A sub-layout is displayed for the user to select one of these items from the adapter that is associated with the current view. There are two kinds of view modes, one is Dropdown, and the other is Dialog.
Second, the XML attribute
Third, the construction method
IV. Case: Choosing a city
MainActivity.java
Activity_main.xml
Pressure Transducer is a device or device that can sense Pressure signals and convert them into usable output electrical signals according to a certain law.Piezoresistive sensor is an ideal sensor for this purpose. For example, it is used to measure the airflow pressure distribution of the helicopter wing, test the dynamic distortion of the engine air inlet, the pulsating pressure of the cascade and the jitter of the wing. A specially designed silicon pressure sensor is used to measure the central pressure of jet engine, and its working temperature is above 500℃. A silicon pressure sensor with an accuracy of 0.05% is used in Boeing's atmospheric data measurement system. The piezoresistive sensors can be densely installed at the inlet of the wind tunnel and in the model of the engine inlet pipe in the model of the downsized wind tunnel model. The single sensor is only 2.36 mm in diameter and has a natural frequency of up to 300 KHZ, with nonlinearity and hysteresis of ±0.22% of the full range. In biomedicine, piezoresistive sensors are also ideal detection tools. The needle type piezoresistive pressure sensors and sensors which can measure pressure in cardiovascular, intracranial, urethra, uterus and eyeball have been made. Figure 3 is a schematic of a sensor used to measure brain pressure. Piezoresistive sensors are also used effectively in the measurement of explosion pressure and shock wave, vacuum measurement, monitoring and control of the performance of automotive engines, as well as in the measurement of weapons such as gun bore pressure, launch shock wave and other measurements. In addition, piezoresistive sensors are widely used in oil well pressure measurement, direction finding while drilling and detection of fault points of underground sealing cables, as well as flow and liquid level measurement. With the further development of microelectronics and computer, the applications of piezoresistive sensors will develop rapidly
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