《第一行代码》第三章

《第一行代码》第三章

目录
  • 《第一行代码》第三章
    • 控件篇
      • TextView
      • Button
      • TextView
      • ImageView
      • ProgressDialog
      • ListView
      • 定制ListView
      • 更强大的滚动控件——RecyclerView
        • 横向
        • 瀑布流
    • 布局篇
      • 线性布局——LinearLayout
      • 相对布局——RelativeLayout
      • 帧布局——FrameLayout
      • 百分比布局
    • 自定义
      • 自定义布局

界面编写实践——聊天界面在下一篇

控件篇

TextView

  • 简单介绍了TextView的几个属性，其余可查阅文档即可

  • "match_parent" 为适应父布局, "wrap_content" 为刚好包住文字，即文字大小

  • android:gravity="center" 设置文本位置; android:textSize="24sp" 设置文字大小，以sp为单位; android:textColor="#00ff00" 设置颜色。

Button

  • 略

TextView

  •

  • android:hint="Type something here" 为提示信息;android:maxLines="2" 为最大行数。

ImageView

  • 修改主活动代码，完成以下效果：

    展开查看 
     private EditText editText;
    private ImageView imageView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(this);
        imageView = (ImageView) findViewById(R.id.image_view);
        editText = (EditText) findViewById(R.id.edit_text);
}@Override
public void onClick(View view) {
    switch (view.getId()) {
        case R.id.button:
            imageView.setImageResource(R.drawable.img_2);
            break;
        default:
            break;
    }
}
  •

  • 所有的Android 控件都可以通过android：visibility 进行指定，可选值有三种：visible、invisible 、gone。gone 表示控件不仅不可见，而且不在占用任何屏幕空间。

  • 使用 setVisibility()方法可以传入 View.VISIBLE、View.INVISIBLE、View.GONE 来控制可见性。

  • 修改主活动case，完成以下效果：

    展开查看
    case R.id.button:
                int progress = progressBar.getProgress();
                progress = progress + 10;
                progressBar.setProgress(progress);
                break;

  • 通过AlerDialog.Builder 创建一个AlertDialog 的实例，然后可以为这个对话框设置标题、内容、可否取消等属性。

  • 修改case：

    case R.id.button:
    AlertDialog.Builder dialog = new AlertDialog.Builder(MainActivity.this);
    dialog.setTitle("This is Dialog");
    dialog.setMessage("Something important.");
    dialog.setCancelable(false);
    dialog.setPositiveButton("OK",new DialogInterface.OnClickListener(){	//设置确定按钮
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
        }
    });
    dialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {	//设置取消按钮
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
        }
    });
    dialog.show();
    break;

ProgressDialog

  • 修改case：

    case R.id.button:
    ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
    progressDialog.setTitle("This is a ProgressDialog");
    progressDialog.setCancelable(true);	//设为true即返回就取消
    progressDialog.show();
    break;

ListView

  • 主活动：

    展开查看 
     
public class MainActivity extends AppCompatActivity {
    private String[] data = {
            "Apple","aa","bb","cc","dd","ee","ff","gg","aa","bb","cc","aa","bb","cc","aa","bb","cc"
    };
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ArrayAdapter adapter = new ArrayAdapter(
            MainActivity.this, android.R.layout.simple_list_item_1, data);
    ListView listView = (ListView) findViewById(R.id.list_view);
    listView.setAdapter(adapter);
}
}

定制ListView

  • 写Fruit类

    展开查看 
     
package com.example.ullayouttest;
public class Fruit {
    private String name;
    private  int imageId;
    public Fruit(String name,int imageId){
        this.name = name;
        this.imageId = imageId;
    }
    public String getName(){
        return name;
    }
    public int getImageId(){
        return imageId;
    }
}

  • 重写适配器

    public class FruitAdapter extends ArrayAdapter {
    private int resourceId;
    public FruitAdapter(Context context, int textViewResourceId, List objects){
        super(context,textViewResourceId,objects);
        resourceId = textViewResourceId;
    }
    public View getView(int position, View convertView, ViewGroup parent){
        Fruit fruit = getItem(position);
        View view = LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
       //以下布局里传入图片与名字
        ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
        TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);
        fruitImage.setImageResource(fruit.getImageId());
        fruitName.setText(fruit.getName());
        return view;
    }
}

  • 修改主活动：

    public class MainActivity extends AppCompatActivity {
    private List fruitList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //主要
        initFruits();
        FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
        ListView listView = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);
        //放进ListView
    }
    private void initFruits(){
        for (int i=0;i<2;i++){
            Fruit 南瓜 = new Fruit("南瓜",R.drawable.nangua);
            fruitList.add(南瓜);
            Fruit 土豆 = new Fruit("土豆",R.drawable.tudou);
            fruitList.add(土豆);
            Fruit 芒果 = new Fruit("芒果",R.drawable.mangguo);
            fruitList.add(芒果);
            Fruit 菠萝 = new Fruit("菠萝",R.drawable.boluo);
            fruitList.add(菠萝);
            Fruit 蘑菇 = new Fruit("蘑菇",R.drawable.mogu);
            fruitList.add(蘑菇);
            Fruit 西瓜 = new Fruit("西瓜",R.drawable.xigua);
            fruitList.add(西瓜);
            Fruit 饮料 = new Fruit("饮料",R.drawable.yinliao);
            fruitList.add(饮料);
        }
    }
}

  • 布局fruit_item：

    <?xml version="1.0" encoding="utf-8"?>

  • 主布局：

    <?xml version="1.0" encoding="utf-8"?>

   />

  • 修改主活动，优化并加入点击事件（程序不久后自动退出了？？）

    public class MainActivity extends AppCompatActivity {
    private List fruitList = new ArrayList<>();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //主要
        initFruits();
        FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
        ListView listView = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Fruit fruit = fruitList.get(position);
                Toast.makeText(MainActivity.this,fruit.getName(),
                        Toast.LENGTH_SHORT).show();

            }
        });
    }

更强大的滚动控件——RecyclerView

  • 修改主活动中onCreate

    public class MainActivity extends AppCompatActivity {
    private List fruitList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //主要
        initFruits();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rc_list);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
       recyclerView.setLayoutManager(layoutManager);
        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);

    }

  • 修改FruitAdapter:

    展开
    
package com.example.ullayouttest;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.List;
public class FruitAdapter extends RecyclerView.Adapter {
    private List mFruitList;
    static class ViewHolder extends RecyclerView.ViewHolder{
        ImageView fruitImage;
        TextView fruitName;
        public ViewHolder(View view){
            super(view);
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView)view.findViewById(R.id.fruit_name);
        }
    }
    public FruitAdapter(List fruitList){
        mFruitList = fruitList;
    }
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())          .inflate(R.layout.fruit_item,parent,false);
        ViewHolder holder = new ViewHolder(view);
        return holder;
    }
    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position); holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }
    @Override
    public int getItemCount() {
        return mFruitList.size();
    }
}

  • 主布局(书里的是android.support.xxx)：

    <?xml version="1.0" encoding="utf-8"?>

/>

横向

  • 修改fruit_item 布局

    <?xml version="1.0" encoding="utf-8"?>

  • 在主活动OnCreate中添加 layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL); 语句

瀑布流

  • 修改主活动，修改的主要代码只有一句，即 StaggeredGridLayoutManager layoutManager 修改成瀑布流。

    展开
    
public class MainActivity extends AppCompatActivity {
    private List fruitList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruits();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rc_list);
        StaggeredGridLayoutManager layoutManager = new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
       recyclerView.setLayoutManager(layoutManager);
        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);
    }
    private void initFruits(){
        for (int i=0;i<2;i++){
            Fruit 南瓜 = new Fruit( getRandomLengthName("南瓜"),R.drawable.nangua);
            fruitList.add(南瓜);
            Fruit 土豆 = new Fruit(getRandomLengthName("土豆"),R.drawable.tudou);
            fruitList.add(土豆);
            Fruit 芒果 = new Fruit(getRandomLengthName("芒果"),R.drawable.mangguo);
            fruitList.add(芒果);
            Fruit 菠萝 = new Fruit(getRandomLengthName("菠萝"),R.drawable.boluo);
            fruitList.add(菠萝);
            Fruit 蘑菇 = new Fruit(getRandomLengthName("蘑菇"),R.drawable.mogu);
            fruitList.add(蘑菇);
            Fruit 西瓜 = new Fruit(getRandomLengthName("西瓜"),R.drawable.xigua);
            fruitList.add(西瓜);
            Fruit 饮料 = new Fruit(getRandomLengthName("饮料"),R.drawable.yinliao);
            fruitList.add(饮料);
        }
    }
    private String getRandomLengthName(String name){
        Random random = new Random();
        int length = random.nextInt(20) + 1;
        StringBuilder builder = new StringBuilder();
        for(int i = 0;i

  • 瀑布流添加事件：与ListView有所不同，需要给子项具体的View添加点击事件

    展开
    
public class FruitAdapter extends RecyclerView.Adapter {
    private List mFruitList;
    static class ViewHolder extends RecyclerView.ViewHolder{
        View fruitView;
        ImageView fruitImage;
        TextView fruitName;
        public ViewHolder(View view){
            super(view);
            fruitView = view;
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView)view.findViewById(R.id.fruit_name);
        }
    }
    public FruitAdapter(List fruitList){
        mFruitList = fruitList;
    }
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
               .inflate(R.layout.fruit_item,parent,false);
        final ViewHolder holder = new ViewHolder(view);
        holder.fruitView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int position = holder.getAdapterPosition();
                Fruit fruit = mFruitList.get(position);
                Toast.makeText(view.getContext(),"you clicked view"+fruit.getName(),Toast.LENGTH_SHORT).show();
            }
        });
        holder.fruitImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int position = holder.getAdapterPosition();
                Fruit fruit = mFruitList.get(position);
                Toast.makeText(view.getContext(),"you clicked image"+fruit.getName(),Toast.LENGTH_SHORT).show();
            }
        });
        return holder;
    }
    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position);
        holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }
    @Override
    public int getItemCount() {
        return mFruitList.size();
    }
}

布局篇

线性布局——LinearLayout

  • 通过 android:orientation="vertical" 可改变为水平排列布局。

  • android:layout_gravity 用于指定控件在布局中的对齐方式。

  • android:layout_weight 可使用比例的方式来指定控件的大小。

相对布局——RelativeLayout

  • 
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_centerInParent="true"

  • 
android:layout_above="@id/button3"
android:layout_toLeftOf="@id/button3"
android:layout_below="@id/button3"
android:layout_toRightOf="@id/button3"

            

帧布局——FrameLayout

  • 所有的控件都默认摆放在布局的左上角

百分比布局

  • 百分比布局————android.support.percent.PercentFrameLayout

    layout_widthPercent="50%"
layout_heightPercent="50%"

自定义

自定义布局

  • 当要添加标题栏，主活动中：

    ActionBar actionBar = getSupportActionBar();
if(actionBar != null){
    actionBar.hide();
    
}

  • 主活动布局添加：

  • 布局：

    android:background="@drawable/title"

自定义控件

  1. 添加新的布局

    <?xml version="1.0" encoding="utf-8"?>

  2. 新建活动并写好相应的功能

    展开查看
    
package com.example.ullayouttest;
import android.app.Activity;
import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;
public class TitleLayout extends LinearLayout {
    public TitleLayout(Context context, AttributeSet attrs){
        super(context,attrs);
        LayoutInflater.from(context).inflate(R.layout.title,this);
        Button titleBack = (Button) findViewById(R.id.back);
        Button titleEdit = (Button) findViewById(R.id.edit);
        titleBack.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                ((Activity)getContext()).finish();
            }
        });
        titleEdit.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(getContext(), "you clicked edit button", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

  3. 接下来当作普通控件使用即可
《第一行代码》总结

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