we found the landscape could not show right in andriod render mode, but it’s okay in ios mode. does this means it could NOT be support well in Andriod platform?
It should work. Though it is hard to say what is going wrong in your case without an image or more details.
Landscape on Android (OpenGL ES2) is limited to 3 texture samplers per section. If you have a section where enough layers overlap that requires more than 3 textures, it won’t build. I recommend packing the red and green normals for your normal maps into a standard texture (RGBA, the alpha channel will be uncompressed, thus, the highest quality). Then, in the material, append the RG values, subtract 0.5, multiply by 2, then Derive Normal Z. You can get 2 normal maps from one texture sampler this way.
You can also do something similar with diffuse textures: if you notice a channel does not have too much variance and shows up as a fairly constant value, you can replace it with a constant and still keep some color variance: just with one or two channels instead of 3. You can derive roughness values from a color channel, if you have to. Just be wary of the SRGB gamma space: linear color textures should be multiplied by themselves (or more accurately raised to a power of 2.19) to avoid appearing washed out. Converting backwards from an SRGB texture to a linear mask (roughness, normal settings, etc) you need to raise to a power of 0.5.
Working with tight texture limitations means you have to get creative with channel packing. A landscape I’m currently making for a mobile game has two normal maps in one texture sampler and the diffuse for two separate layers in another.