android中实现底部导航栏

1、引言

        底部导航栏在app应用中是十分常见了，大部分的安卓应用中也都实现了底部导航栏的功能，这里我就以我以前做的一个简单小说阅读软件为例，为大家演示一下底部导航栏的使用，需要的朋友直接复制代码过去改写就行了。

2、代码实现

2.1、主界面布局

2.2、主界面代码

        这里包含了一些进行操作实际功能的代码，大家复制时直接忽略就行。

package com.kotlin.novel;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.fragment.app.FragmentTransaction;

import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.View;
import android.widget.RadioGroup;
import android.widget.Toast;

import com.google.gson.Gson;
import com.kotlin.base.BaseFragment;
import com.kotlin.data.UpdateVersion;
import com.kotlin.dialog.UpdateDialogActivity;
import com.kotlin.fragment.BookShelfFragment;
import com.kotlin.fragment.BookStoreFragment;
import com.kotlin.fragment.UserFragment;
import com.kotlin.utils.ServerUtils;
import com.kotlin.utils.SetUiSize;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

/**
 * 主界面导航切换，如果需要添加界面来这里修改
 */
public class MainActivity extends FragmentActivity {
    @Override
    protected void onResume() {//强制竖屏
        if (getRequestedOrientation()!=ActivityInfo.SCREEN_ORIENTATION_PORTRAIT){
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        }
        super.onResume();
    }
    public static MainActivity activity;
    public RadioGroup rg_main;
    private List baseFragment;
    private int position;//选中的Fragment的对应的位置
    private Fragment fragment;//上次切换的Fragment
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        View decorView=getWindow().getDecorView();//获取当前界面的DecorView
        int option=View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN |
                View.SYSTEM_UI_FLAG_LAYOUT_STABLE |//全屏隐藏状态栏
                View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR;//更改文字颜色为深黑色
        decorView.setSystemUiVisibility(option);//设置系统UI元素的可见性
        getWindow().setNavigationBarColor(Color.TRANSPARENT);
        getWindow().setStatusBarColor(Color.TRANSPARENT);//将状态栏设置为透明色
        rg_main = findViewById(R.id.rg_main);
        initFragment();
        setListener();
        activity=this;
        updateVersion();
    }
    private void setListener() {
        rg_main.setOnCheckedChangeListener(new CheckedChangeListener());
        //设置默认选中书架
        rg_main.check(R.id.rb_main_book);
    }
    class CheckedChangeListener implements RadioGroup.OnCheckedChangeListener {
        @Override
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            switch (checkedId){
                case R.id.rb_main_book://书架
                    position = 0;
                    break;
                case R.id.rb_main_store://书城
                    position = 1;
                    break;
                case R.id.rb_main_user://我的
                    position = 2;
                    break;
            }
            //根据位置得到对应的Fragment
            BaseFragment to = getFragment();
            //替换
            switchFrament(fragment,to);
        }
    }
    /**
     * @param from 刚显示的Fragment,马上就要被隐藏
     * @param to 马上要切换到的Fragment，马上就要被显示
     */
    private void switchFrament(Fragment from,Fragment to) {
        if(from != to){
            fragment = to;
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            //判断有没有被添加,才切换
            if(!to.isAdded()){
                //to没有被添加
                //from隐藏
                if(from != null){
                    ft.hide(from);
                }
                //添加to
                if(to != null){
                    ft.add(R.id.fl_content,to).commit();
                }
            }else{
                //to已经被添加
                // from隐藏
                if(from != null){
                    ft.hide(from);
                }
                //显示to
                if(to != null){
                    ft.show(to).commit();
                }
            }
        }
    }
    /**
     * 根据位置得到对应的Fragment
     * @return
     */
    private BaseFragment getFragment() {
        BaseFragment fragment = baseFragment.get(position);
        return fragment;
    }
    private void initFragment() {
        baseFragment = new ArrayList<>();
        baseFragment.add(new BookShelfFragment());//书架Fragment
        baseFragment.add(new BookStoreFragment());//书城Fragment
        baseFragment.add(new UserFragment());//我的Fragment
    }
    public boolean exit;//标识是否可以退出
    @Override
    public boolean onKeyUp(int keyCode, KeyEvent event) {
        if(event.getKeyCode()==KeyEvent.KEYCODE_BACK) {
            if(exit) {
                BookShelfFragment.fragment.handler.sendEmptyMessage(1);//刷新书架，取消选择
                return true;//不退出
            }
        }
        return super.onKeyUp(keyCode, event);
    }
    private String result;
    /**
     * 获取更新数据
     */
    private void updateVersion(){
        new Thread(){
            @Override
            public void run() {
                URL url;
                try {
                    url=new URL(ServerUtils.updatePath);
                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    connection.setReadTimeout(5000);
                    connection.setConnectTimeout(5000);
                    int code = connection.getResponseCode();
                    if (code==200){
                        InputStream is = connection.getInputStream();
                        ByteArrayOutputStream bs=new ByteArrayOutputStream();
                        int len=-1;
                        byte[] buffer=new byte[1024];
                        while ((len=is.read(buffer))!=-1){
                            bs.write(buffer,0,len);
                        }
                        result = bs.toString();
                        bs.close();
                        is.close();
                        connection.disconnect();
                    }
                } catch (Exception e) {
                }
                if (result!=null&&!result.equals("")){
                    handler.sendEmptyMessage(0);
                }
            }
        }.start();
    }
    /**
     * 提示
     * @param message
     */
    private void tip(String message){
        runOnUiThread(() -> {
            //更改默认Toast显示方式，需要什么直接调用方法就行
            Toast toast=Toast.makeText(MainActivity.this,
                    message,Toast.LENGTH_SHORT);
            int size= (int) (280/ SetUiSize.displayHeightDp*SetUiSize.displayHeight);
            toast.setGravity(Gravity.TOP,
                    0,size);
            toast.show();
        });
    }
    private Handler handler=new Handler(){
        @Override
        public void handleMessage(@NonNull Message msg) {
            super.handleMessage(msg);
            switch (msg.what){
                case 0:
                {
                    UpdateVersion version = new Gson().fromJson(result, UpdateVersion.class);
                    if (version.getApk_version()>ServerUtils.versionCode){
                        Intent intent=new Intent(MainActivity.this, UpdateDialogActivity.class);
                        intent.putExtra("result",result);
                        startActivity(intent);
                    }
                }
                break;
            }
        }
    };
}

2.3、自定义控件

        自定义radiobutton:

package com.kotlin.custom;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.RadioButton;

import com.kotlin.novel.R;
/**
 * Describe：可控制drawableTop等图片的大小
 */
@SuppressLint("AppCompatCustomView")
public class DrawableRadioButton extends RadioButton {
    private int mDrawableSize;// xml文件中设置的大小
    public DrawableRadioButton(Context context) {
        this(context, null, 0);
    }
    public DrawableRadioButton(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }
    public DrawableRadioButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        Drawable drawableLeft = null, drawableTop = null, drawableRight = null, drawableBottom = null;
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.DrawableRadioButton);
        int n = a.getIndexCount();
        for (int i = 0; i < n; i++) {
            int attr = a.getIndex(i);
            switch (attr) {
                case R.styleable.DrawableRadioButton_drawableSize:
                    mDrawableSize = a.getDimensionPixelSize(R.styleable.DrawableRadioButton_drawableSize, 50);
                    break;
                case R.styleable.DrawableRadioButton_drawableTop:
                    drawableTop = a.getDrawable(attr);
                    break;
                case R.styleable.DrawableRadioButton_drawableBottom:
                    drawableRight = a.getDrawable(attr);
                    break;
                case R.styleable.DrawableRadioButton_drawableRight:
                    drawableBottom = a.getDrawable(attr);
                    break;
                case R.styleable.DrawableRadioButton_drawableLeft:
                    drawableLeft = a.getDrawable(attr);
                    break;
            }
        }
        a.recycle();
        setCompoundDrawablesWithIntrinsicBounds(drawableLeft, drawableTop, drawableRight, drawableBottom);
    }
    /**
     * RadioButton上、下、左、右设置图标
     */
    public void setCompoundDrawablesWithIntrinsicBounds(Drawable left, Drawable top, Drawable right, Drawable bottom) {
        if (left != null) {
            left.setBounds(0, 0, mDrawableSize, mDrawableSize);
        }
        if (right != null) {
            right.setBounds(0, 0, mDrawableSize, mDrawableSize);
        }
        if (top != null) {
            top.setBounds(0, 0, mDrawableSize, mDrawableSize);
        }
        if (bottom != null) {
            bottom.setBounds(0, 0, mDrawableSize, mDrawableSize);
        }
        setCompoundDrawables(left, top, right, bottom);
    }
}

        自定义圆形图标。

package com.kotlin.custom;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.*;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import com.kotlin.novel.R;

public class CircleImageView extends androidx.appcompat.widget.AppCompatImageView {
    private static final ScaleType SCALE_TYPE = ScaleType.CENTER_CROP;
    private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888;
    private static final int COLORDRAWABLE_DIMENSION = 1;
    private static final int DEFAULT_BORDER_WIDTH = 0;
    private static final int DEFAULT_BORDER_COLOR = Color.BLACK;
    private final RectF mDrawableRect = new RectF();
    private final RectF mBorderRect = new RectF();
    private final Matrix mShaderMatrix = new Matrix();
    private final Paint mBitmapPaint = new Paint();
    private final Paint mBorderPaint = new Paint();
    private int mBorderColor = DEFAULT_BORDER_COLOR;
    private int mBorderWidth = DEFAULT_BORDER_WIDTH;
    private Bitmap mBitmap;
    private BitmapShader mBitmapShader;
    private int mBitmapWidth;
    private int mBitmapHeight;
    private float mDrawableRadius;
    private float mBorderRadius;
    private boolean mReady;
    private boolean mSetupPending;
    public CircleImageView(Context context) {
        super(context);
    }
    public CircleImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }
    public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        super.setScaleType(SCALE_TYPE);
        TypedArray a = context.obtainStyledAttributes(attrs,
                R.styleable.CircleImageView, defStyle, 0);
        mBorderWidth = a.getDimensionPixelSize(
                R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH);
        mBorderColor = a.getColor(R.styleable.CircleImageView_border_color,
                DEFAULT_BORDER_COLOR);
        a.recycle();
        mReady = true;
        if (mSetupPending) {
            setup();
            mSetupPending = false;
        }
    }
    @Override
    public ScaleType getScaleType() {
        return SCALE_TYPE;
    }
    @Override
    public void setScaleType(ScaleType scaleType) {
        if (scaleType != SCALE_TYPE) {
            throw new IllegalArgumentException(String.format(
                    "ScaleType %s not supported.", scaleType));
        }
    }
    @Override
    protected void onDraw(Canvas canvas) {
        if (getDrawable() == null) {
            return;
        }
        canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius,
                mBitmapPaint);
        if (mBorderWidth != 0) {
            canvas.drawCircle(getWidth() / 2, getHeight() / 2, mBorderRadius,
                    mBorderPaint);
        }
    }
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        setup();
    }
    public int getBorderColor() {
        return mBorderColor;
    }
    public void setBorderColor(int borderColor) {
        if (borderColor == mBorderColor) {
            return;
        }
        mBorderColor = borderColor;
        mBorderPaint.setColor(mBorderColor);
        invalidate();
    }
    public int getBorderWidth() {
        return mBorderWidth;
    }
    public void setBorderWidth(int borderWidth) {
        if (borderWidth == mBorderWidth) {
            return;
        }
        mBorderWidth = borderWidth;
        setup();
    }
    @Override
    public void setImageBitmap(Bitmap bm) {
        super.setImageBitmap(bm);
        mBitmap = bm;
        setup();
    }
    @Override
    public void setImageDrawable(Drawable drawable) {
        super.setImageDrawable(drawable);
        mBitmap = getBitmapFromDrawable(drawable);
        setup();
    }
    @Override
    public void setImageResource(int resId) {
        super.setImageResource(resId);
        mBitmap = getBitmapFromDrawable(getDrawable());
        setup();
    }
    private Bitmap getBitmapFromDrawable(Drawable drawable) {
        if (drawable == null) {
            return null;
        }
        if (drawable instanceof BitmapDrawable) {
            return ((BitmapDrawable) drawable).getBitmap();
        }
        try {
            Bitmap bitmap;
            if (drawable instanceof ColorDrawable) {
                bitmap = Bitmap.createBitmap(COLORDRAWABLE_DIMENSION,
                        COLORDRAWABLE_DIMENSION, BITMAP_CONFIG);
            } else {
                bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(),
                        drawable.getIntrinsicHeight(), BITMAP_CONFIG);
            }
            Canvas canvas = new Canvas(bitmap);
            drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
            drawable.draw(canvas);
            return bitmap;
        } catch (OutOfMemoryError e) {
            return null;
        }
    }
    private void setup() {
        if (!mReady) {
            mSetupPending = true;
            return;
        }
        if (mBitmap == null) {
            return;
        }
        mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
        mBitmapPaint.setAntiAlias(true);
        mBitmapPaint.setShader(mBitmapShader);
        mBorderPaint.setStyle(Paint.Style.STROKE);
        mBorderPaint.setAntiAlias(true);
        mBorderPaint.setColor(mBorderColor);
        mBorderPaint.setStrokeWidth(mBorderWidth);
        mBitmapHeight = mBitmap.getHeight();
        mBitmapWidth = mBitmap.getWidth();
        mBorderRect.set(0, 0, getWidth(), getHeight());
        mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2,
                (mBorderRect.width() - mBorderWidth) / 2);
        mDrawableRect.set(mBorderWidth, mBorderWidth, mBorderRect.width()
                - mBorderWidth, mBorderRect.height() - mBorderWidth);
        mDrawableRadius = Math.min(mDrawableRect.height() / 2,
                mDrawableRect.width() / 2);
        updateShaderMatrix();
        invalidate();
    }
    private void updateShaderMatrix() {
        float scale;
        float dx = 0;
        float dy = 0;
        mShaderMatrix.set(null);
        if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width()
                * mBitmapHeight) {
            scale = mDrawableRect.height() / (float) mBitmapHeight;
            dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
        } else {
            scale = mDrawableRect.width() / (float) mBitmapWidth;
            dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
        }
        mShaderMatrix.setScale(scale, scale);
        mShaderMatrix.postTranslate((int) (dx + 0.5f) + mBorderWidth,
                (int) (dy + 0.5f) + mBorderWidth);
        mBitmapShader.setLocalMatrix(mShaderMatrix);
    }
}

        自定义控件的attrs文件。

3、效果

3.1、书架页面

3.2、书城页面

3.3、我的页面