2.4 学习总计之自己实现底部导航

说在前面

昨天	完成了分页查询展示数据
今天	学习底部导航的实现过程

一、相关知识

1、底部所导航的几个界面是相互独立的，没有前后层次关系。

二、构建导航框架

1、构建三个静态页面结构（Fragment）和相应的ViewModel（保存UI数据）。

2、创建底部导航（实质是一个菜单）。

1）创建一个菜单，添加三个MenuItem

2）在main_activity.xml中拖一个：

3）将菜单加入

4）移动到底部

3、创建一个navigation组件，用来三个页面进行动态的切换等管理。

注意事项：界面的id，和菜单中MenuItem的id相同

界面：

菜单项：

1）完善界面

2）导入界面

3）在main_activity.xml中拖一个：

并关联刚才的navigation

三、完善逻辑结构

1、完成界面切换（装配BottomNavigationView和NAVHostFragment）

MainActive.java

package com.example.bottomnavigationdemo;

import androidx.appcompat.app.AppCompatActivity;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;

import android.os.Bundle;

import com.google.android.material.bottomnavigation.BottomNavigationView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        BottomNavigationView bottomNavigationView = findViewById(R.id.bottomNavigationView);
        NavController navController = Navigation.findNavController(this,R.id.fragment);
        AppBarConfiguration configuration = new AppBarConfiguration.Builder(bottomNavigationView.getMenu()).build();
        NavigationUI.setupActionBarWithNavController(this,navController,configuration);
        NavigationUI.setupWithNavController(bottomNavigationView,navController);
    }
}

2、设置各个界面的功能

1）旋转 FirstFragment.java 实现动作，FirstViewModel.java保存数据

package com.example.bottomnavigationdemo;

import android.animation.ObjectAnimator;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.ViewModelProviders;


public class FirstFragment extends Fragment {
    private static final String TAG = "hello";
    private FirstViewModel mViewModel;
    private ImageView imageView;

    public static FirstFragment newInstance() {
        return new FirstFragment();
    }


    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.first_fragment, container, false);
        imageView = view.findViewById(R.id.imageView);
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        mViewModel = ViewModelProviders.of(requireActivity()).get(FirstViewModel.class);
        imageView.setRotation(mViewModel.rotationPosition);
        final ObjectAnimator objectAnimator = ObjectAnimator.ofFloat(imageView, "rotation", 0, 0);
        objectAnimator.setDuration(500);
        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!objectAnimator.isRunning()) {
                    objectAnimator.setFloatValues(imageView.getRotation(), imageView.getRotation() + 100);
                    mViewModel.rotationPosition += 100;
                    objectAnimator.start();
                }
            }
        });
    }

}

package com.example.bottomnavigationdemo;

import androidx.lifecycle.ViewModel;

public class FirstViewModel extends ViewModel {
    // TODO: Implement the ViewModel
    float rotationPosition = 0;
}

2）缩放 SecondFragment.java 实现动作，SecondViewModel.java保存数据

package com.example.bottomnavigationdemo;

import android.animation.ObjectAnimator;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.ViewModelProviders;

public class SecondFragment extends Fragment {

    private SecondViewModel mViewModel;
    private ImageView imageView;

    public static SecondFragment newInstance() {
        return new SecondFragment();
    }

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.second_fragment, container, false);
        imageView = view.findViewById(R.id.imageView);
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        mViewModel = ViewModelProviders.of(requireActivity()).get(SecondViewModel.class);
        imageView.setScaleX(mViewModel.scaleFactor);
        imageView.setScaleY(mViewModel.scaleFactor);
        // TODO: Use the ViewModel
        final ObjectAnimator objectAnimatorX = ObjectAnimator.ofFloat(imageView, "scaleX", 0, 0);
        final ObjectAnimator objectAnimatorY = ObjectAnimator.ofFloat(imageView, "scaleY", 0, 0);
        objectAnimatorX.setDuration(500);
        objectAnimatorY.setDuration(500);
        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!objectAnimatorX.isRunning()) {
                    objectAnimatorX.setFloatValues(imageView.getScaleX() + 0.1f);
                    objectAnimatorY.setFloatValues(imageView.getScaleY() + 0.1f);
                    mViewModel.scaleFactor += 0.1;
                    objectAnimatorX.start();
                    objectAnimatorY.start();
                }
            }
        });

    }

}

package com.example.bottomnavigationdemo;

import androidx.lifecycle.ViewModel;

public class SecondViewModel extends ViewModel {
    // TODO: Implement the ViewModel
    float scaleFactor = 1;
}

3）移动 ThirdFragment.java 实现动作，ThirdViewModel.java保存数据

package com.example.bottomnavigationdemo;

import android.animation.ObjectAnimator;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.ViewModelProviders;

import java.util.Random;

public class ThirdFragment extends Fragment {

    private ThirdViewModel mViewModel;
    private ImageView imageView;

    public static ThirdFragment newInstance() {
        return new ThirdFragment();
    }

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.third_fragment, container, false);
        imageView = view.findViewById(R.id.imageView);
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        mViewModel = ViewModelProviders.of(requireActivity()).get(ThirdViewModel.class);
        imageView.setX(imageView.getX() + mViewModel.dX);
        // TODO: Use the ViewModel
        final ObjectAnimator objectAnimator = ObjectAnimator.ofFloat(imageView, "x", 0, 0);
        objectAnimator.setDuration(500);
        imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!objectAnimator.isRunning()) {
                    float dx = new Random().nextBoolean() ? 100 : -100;
                    objectAnimator.setFloatValues(imageView.getX(), imageView.getX() + dx);
                    mViewModel.dX += dx;
                    objectAnimator.start();
                }
            }
        });
    }

}

package com.example.bottomnavigationdemo;

import androidx.lifecycle.ViewModel;

public class ThirdViewModel extends ViewModel {
    // TODO: Implement the ViewModel
    float dX;
}

2.4 学习总计 之 自己实现底部导航