In the first battle, we created the first app project

Previously summary (previously)

In the first battle, we created the first app project, HelloWorld, and analyzed the project structure and how it works.

Link here: Android Studio single Brush The first line of code series 01--First Battle HelloWorld

Summary (abstract)

Required skills, use the Log tool LogCat, and try to solve the problem of real machine debugging without logs.

Log tool (LogCat)

Logs play a very important role in the development of any project, and in Android projects you have to use the LogCat tool if you want to view the logs.

Find 6:android in the Status Bar at the bottom of Android Studio and click on her. Such as

1. Choose Devices here, of course, generally do not need to choose, if only one device connected.
2. Here, log level is selected. Includes: Verbose, Debug, Info, Warn, Error, Assert. The above levels are raised sequentially.
3. The filter is selected here, and the default is to automatically generate a filter that is the package name is a filter for the project name.

Using LogCat

The Log tool class in Android is log (ANDROID.UTIL.LOG), which provides several ways for us to print the logs.

1. LOG.V () corresponds to Verbose
2. LOG.D () corresponds to Debug
3. LOG.I () corresponding Info
4. LOG.W () corresponds to Warn
5. LOG.E () corresponds to Error
6. LOG.WTF () Prints the execution path (the call stack) at this point in the code at the same time as the output log.

The introduction is over, let's play a little bit. Open helloworldactivity, add a line of print log statements in the Oncreat () method, in order to make the log obvious I added some underscores, as follows:

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In the first battle, we created the first app project