Problems when developing Android apps

Problems when developing Android apps

1, when writing Layout.xml

         <linearlayout xmlns:android= "http://schemas.android.com/apk/res/android"    android:layout_width= "Match_ Parent "    android:layout_height=" match_parent "    android:orientation=" vertical "></LinearLayout>

One of the xmlns:android=http://schemas.android.com/apk/res/android must have. Otherwise androidxml parser will prompt for the missing prefix Android error. So if you're writing layout.xml yourself, be sure to remember to add XML namespaces.

2. File->new->androidapplication project in Eclipse, using the default configuration, there will be one more project "Appcompat_v7" in Eclipse. The Android SDK I downloaded was Android 4.4.2 API19, and looked at the data as if it were a compatible package that Google used to be compatible with the previous Android2.1 version of the interface. The first is the red exclamation point, as shown in:

In fact, this project can be compiled successfully, we need to Project->clean...->clean project selected below in Eclipse to select Appcompat_v7, and then build, this will become the X number, Then clean, and then compile, just fine. And our main project relies on it, and it can be successfully compiled.