0 Preface
The original meaning of the word Android refers to "robot", and it is also the name of the open source mobile terminal operating system based on the Linux platform announced by Google on November 5, 2007. The platform consists of the operating system, middleware, user interface and application software It is the first truly open and complete mobile software for mobile terminals.
With the continuous development of technology, mobile phones are no longer just mobile communication tools for people's daily lives, but a multimedia platform that provides powerful multimedia functions. More and more people like to use their mobile phones to listen to music and watch movies. The music player built into the Android system manages songs based on the media library, and does not support synchronized display of lyrics. For some users who are already accustomed to the player based on the file browser, the operation will be inconvenient. For the Android mobile phone operating system, you can make full use of its rich programmability and develop new player application software.
1 Android platform
Android software development mainly involves related technologies including Android SDK (development plug-in, debugging toolkit, etc.), Android system architecture and Android application components.
1.1 Android SDK
The Android SDK (Software Development Kit) provides API interfaces and tools for Android application development using the Java language on the Android platform. Among them, the most important tool is the Android emulator and its plug-in for the Android developer of Eclipse. At the same time, the SDK also contains various tools for debugging, packaging and installation on the emulator.
The Eclipse IDE's Android Development Tools Plugin for the Eclipse IDE (ADT) greatly expands the functionality of the Eclipse integrated environment, making it easy and quick to generate and debug Android applications. Using Eclipse, the ADT plug-in can speed up the development of Android applications.
The Android emulator is a virtual mobile device running on a computer. You can use the emulator to simulate an actual Android operating environment to design, debug, and test applications.
Dalvik Debug Monitor Service (Dalvik Debug Monitor Service, DDMS) integrates Dalvik (Virtual Machine (VM) customized for the Android platform), which can manage processes and assist debugging on the emulator or device. DDMS provides process management, generates tracking data, observes heap and thread information, intercepts simulator screens, and simulates incoming calls or text messages.
1.2 Android system architecture
Android is a software set specifically for mobile devices, which includes an operating system, middleware and some important applications. Android's system architecture is from top to bottom, applications, application frameworks and components, Android runtime libraries and other libraries, optimized Linux kernel.
1.3 Components of the Android application
The operating environment of a mobile phone is relatively complicated. When a program is running, there are often many unexpected situations, such as incoming calls or short messages and insufficient power. These problems have solutions in Android, in the Android application, the following components are particularly important:
(1) AcTIvity
As the name suggests, AcTIvity is an activity. The application must contain at least one AcTIvity. AcTIvity provides a virtual user interface. Each Activity has a default window that can be used to display the user interface. In general, it is a full-screen window. For example, each user interface of audio and video playback software is an Activity.
(2) Service
The main difference between Service and Activity is that Service is active in the background, it has no user interface. The typical application scenario is that after the user selects a playlist to start playing and leaves the user interface (Activity), if you still want the song to not pause, you can use Service to call the player instead of calling the player in the Activity .
(3) Intent
In Android, each behavior can be abstracted as an Intent. You can simply understand Intent as a message that contains data. Intent can be used to start an Act-ivity or Service, can be used for inter-process communication. In fact, application startup is also achieved through Intent.
(4) Content providers
The Android platform has a built-in SQLite data storage mechanism and contains a series of related methods for managing SQLite Database. In the application, you can access the database through Content prov-iders. Each Content provider defines a series of methods for accessing its corresponding database. When an application creates a new database, it can also define a corresponding Con-tent provider to share data with other applications. Under normal circumstances, the application does not directly call the function defined by the Content provider, but indirectly through the ContentResolver. The advantage of this design is that a ContentResolver can access any Content provider, unifying the interface.
2 Hardware platform
The hardware platform of the system adopts DevKit8000, a development board based on OMAP3530. TI's OMAP3530 application processor integrates a 600 MHz ARM Cortex-A8 CPU core and a 430 MHz C64x + DSP core, and provides rich peripheral interfaces such as USB 2.OOTG, SD / MMC, and LCD, suitable for Various wireless handheld terminal applications. The DevKit8000 development board is connected with a 4.3-inch LCD screen, resistive touch screen and audio input / output interface, which can be used for the development of audio and video players based on the Android system.
Through patching packages and developing peripheral drivers such as LCD drivers, touch screen drivers, and key drivers, a Linux kernel of version 6.2.29 and an Android system of version 1.6 were ported to the DevKit8000 development board.
3 Android video player software development
3.1 Software functions
Android audio and video playback software mainly includes the following functions:
(1) Play video
Supports fast forward, rewind, pause, continue, and progress dragging.
(2) Play audio
Support fast forward, rewind, previous song, next song, pause, continue, stop and progress dragging; support two modes of random play and loop play; support synchronous lyrics display.
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