Androidc学习笔记二之四大布局及碎片理解用法

android中四大布局、ListView的用法和理解、RecyclerView的用法和理解、android中碎片的理解和用法

android中的四大布局；

LinearLayout(流式布局) 其中学到layout_weight权重值概念权重值概念
relativeLayout(相对布局) 其中layout_alignParentTop/right/left/botton="true"....
layout_above/below="@id/button1" layout_toright/left="@id/button1"
FrameLayout(帧布局) 应用场景太少，基本就是固定模式主要用到gravity(定重心即可)
PercentFrameLayout(百分比布局) 为了解决百分比占用布局的问题而开发出来的，
首先这个需要引库在app/build.gradle文件，dependencies比包下添加内容compile'com.android.support:percent:24.2.1'即可，需要同步一下(Sync Now)
用到layout_gravity、layout_width/heightPercent="40%"来运用百分比。
TableLayout表格布局 AbsoluteLayout绝对布局

可以发现我们再android中使用的空间基本都是直接或者间接继承View的，当然除了自定义控件。

ListView控件:最常用也是最难的控件，主要用于数据的显示(主要是android的屏幕空间能够显示的内容太少了)
ListView用户允许用户上下滑动来展示数据。
通过构建适配器Adapter来构建索要显示的内容最后将适配器设置(ListView.setAdapter(adapter))到listview上去就搭建成功了。

例子：

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

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

FruitBean.classpackage com.example.ldp.com.bean;/** * Created by Administrator on 2017/3/6. */public class FruitBean {    private String name;    private int imageid;    public String getName() {        return name;    }    public FruitBean(String name,int imageid){        this.name = name;        this.imageid = imageid;    }    public int getImageid() {        return imageid;    }}

FruitAdapter.classpackage com.example.ldp.com.bean;import android.content.Context;import android.support.annotation.NonNull;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 com.example.ldp.com.uicustomerviews.R;import java.util.List;/** * Created by Administrator on 2017/3/6. */public class FruitAdapter extends ArrayAdapter {    private int resourceId;    public FruitAdapter(Context context, int textViewResourceId, List objects) {        super(context, textViewResourceId, objects);        resourceId = textViewResourceId;    }    @NonNull    @Override    public View getView(int position, View convertView, ViewGroup parent) {    //convertView用于将之前加载好的布局进行缓存，以便可以重用        FruitBean fruit = getItem(position);//获取当前项的fruit实例        View view;        ViewHolder viewholder;        if(convertView==null){            view = LayoutInflater.from(getContext()).inflate(resourceId,parent,false);            viewholder = new ViewHolder();            viewholder.fruitImage = (ImageView) view.findViewById(R.id.fruit_image);            viewholder.fruitName = (TextView)view.findViewById(R.id.fruit_name);            view.setTag(viewholder);//将viewHolder存储在View中        }else{            view = convertView;//所以当不为空的时候就重用，深化性能            viewholder = (ViewHolder) view.getTag();//重新获取ViewHolder        }        viewholder.fruitImage.setImageResource(fruit.getImageid());        viewholder.fruitName.setText(fruit.getName());        return view;    }    class ViewHolder{        /*第一步是缓存布局converView,第二步是缓存控件，当这个布局存在的情况下        ，自然其中的控件也存在就不用每次都通过findViewById来找实例了，通过这两步实现这个ListView性能优化*/        ImageView fruitImage;        TextView fruitName;    }}

MainActivity.classpackage com.example.ldp.com.uicustomerviews;import android.support.v7.app.ActionBar;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.AdapterView;import android.widget.ArrayAdapter;import android.widget.ListView;import android.widget.Toast;import com.example.ldp.com.bean.FruitAdapter;import com.example.ldp.com.bean.FruitBean;import java.util.ArrayList;import java.util.List;import static android.widget.AdapterView.*;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();//初始化数据        FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);        ListView listView = (ListView) findViewById(R.id.list_view);        listView.setAdapter(adapter);        //相应listView子布局项的响应(监听event)        listView.setOnItemClickListener(new OnItemClickListener() {            @Override            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {                FruitBean fruit =fruitList.get(position);                Toast.makeText(MainActivity.this,fruit.getName()+"您点击了！",Toast.LENGTH_SHORT).show();            }        });    }    private void initFruits(){        for(int i=0;i<2;i++){            FruitBean apple = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple);            FruitBean apple1 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple1);            FruitBean apple2 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple2);            FruitBean apple3 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple3);            FruitBean apple4 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple4);            FruitBean apple5 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple5);            FruitBean apple6 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple6);            FruitBean apple7 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple7);            FruitBean apple8 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple8);            FruitBean apple9 = new FruitBean("Apple",R.drawable.ic_launcher);            fruitList.add(apple9);        }    }}

ListView效果图：

RecycleView(滚动控件)：用它的理由自然是因为ListView的缺点了，
它只能纵向滑动，不能横向滑动，而且又性能缺点，只能采用一些技巧来优化。
当我们需要实现横向功能的时候，就需要用来RecycleView这种滚动控件了。
它即可轻松实现ListView的额工恩能够，也优化了许多的不足。

注:它和百分比一样需要引库才能使用。

build.gradle文件dependencies {    compile 'com.android.support:recyclerview-v7:25.2.0'}

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

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

Fruit.classpackage com.example.ldp.com.bean;/** * Created by Administrator on 2017/3/6. */public class Fruit {    private String name;    private int imageid;    public String getName() {        return name;    }    public Fruit(String name,int imageid){        this.name = name;        this.imageid = imageid;    }    public int getImageid() {        return imageid;    }}

FruitAdapter.classpackage com.example.ldp.com.bean;import android.support.v7.widget.RecyclerView;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;import android.widget.TextView;import com.example.ldp.com.recyclerview.R;import java.util.List;/** * Created by Administrator on 2017/3/6. */public class FruitAdapter extends RecyclerView.Adapter {    private List mfruitLists;    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){        this.mfruitLists=fruitList;    }    @Override    public ViewHolder onCreateViewHolder(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(ViewHolder holder, int position) {        Fruit fruit = mfruitLists.get(position);        holder.fruitImage.setImageResource(fruit.getImageid());        holder.fruitName.setText(fruit.getName());    }    @Override    public int getItemCount() {        return mfruitLists.size();    }}

MainActivity.classpackage com.example.ldp.com.recyclerview;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.widget.LinearLayoutManager;import android.support.v7.widget.RecyclerView;import com.example.ldp.com.bean.Fruit;import com.example.ldp.com.bean.FruitAdapter;import java.util.ArrayList;import java.util.List;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();//初始化数据        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);        LinearLayoutManager layoutManager = new LinearLayoutManager(this);        recyclerView.setLayoutManager(layoutManager);        FruitAdapter adapter = new FruitAdapter(fruitList);        recyclerView.setAdapter(adapter);        //监听    }    private void initFruits(){        for(int i=0;i<2;i++){            Fruit apple = new Fruit("Apple",R.drawable.ic_launcher);//照片和内容            fruitList.add(apple);            Fruit apple1 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple1);            Fruit apple2 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple2);            Fruit apple3 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple3);            Fruit apple4 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple4);            Fruit apple5 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple5);            Fruit apple6 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple6);            Fruit apple7 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple7);            Fruit apple8 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple8);            Fruit apple9 = new Fruit("Apple",R.drawable.ic_launcher);            fruitList.add(apple9);        }    }}

这个的效果图个ListView差不多它就是为了实现ListView的效果而演示的。

若是要将recycleList修改成横向滑动的话只需要在刚才的代码上修改如下代码即可:

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

MainActivity.class
在LinearLayoutManager layoutManager = new LinearLayoutManager(this);下加下面代码即可
layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);//设置横向滑动
这个要得益于LayoutManager布局系列接口，这就是为什么ListView不能实现横向滑动，
而RecyclerList能，因为前者的布局是自身管理，而后者是交给LayoutManager管理。

效果图:

RecycleView的触发事件，相对ListView来说就复杂许多了，试问一下这有是为什么呢？
Recycle的优势那么明显干嘛不把监听也做得很简单呢？ListView是触发一个子项，但是当我们要触发子项当中的某一个按钮的时候咋办？
ListView也可以实现这样的监听，但是实现就会很复杂，所以RecycleView就直接摒弃了
触发子项，直接让触发事件又View来注册。

修改代码：FruitAdapter.class

package com.example.ldp.com.bean;import android.support.v7.widget.RecyclerView;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;import android.widget.TextView;import android.widget.Toast;import com.example.ldp.com.recyclerview.R;import java.util.List;/** * Created by Administrator on 2017/3/6. */public class FruitAdapter extends RecyclerView.Adapter {    private List mfruitLists;    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){        this.mfruitLists=fruitList;    }    @Override    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,parent,false);        final  ViewHolder holder = new ViewHolder(view);        /*监听事件*/        holder.fruitView.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                int position = holder.getAdapterPosition();                Fruit fruit = mfruitLists.get(position);                Toast.makeText(v.getContext(),"Click view  -"+fruit.getName(),Toast.LENGTH_SHORT).show();            }        });        holder.fruitImage.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                int position = holder.getAdapterPosition();                Fruit fruit = mfruitLists.get(position);                Toast.makeText(v.getContext(),"Click image  -",Toast.LENGTH_SHORT).show();            }        });        holder.fruitName.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                int position = holder.getAdapterPosition();                Fruit fruit = mfruitLists.get(position);                Toast.makeText(v.getContext(),"Click name  -"+fruit.getName(),Toast.LENGTH_SHORT).show();            }        });        return holder;    }    @Override    public void onBindViewHolder(ViewHolder holder, int position) {        Fruit fruit = mfruitLists.get(position);        holder.fruitImage.setImageResource(fruit.getImageid());        holder.fruitName.setText(fruit.getName());    }    @Override    public int getItemCount() {        return mfruitLists.size();    }}

对于数据的显示就学习到这里，ListView和RecycleView需要深入学习，这是一个复杂很难懂的知识点儿，说实话我也没学懂。

效果图：

碎片
碎片是一种可以嵌入到活动当中的UI片段，它能让程序更加合理的去使用大屏幕空间
(这就有点儿类似web当中的响应式布局了)当我们在小屏幕上设计的美美的UI，到了大屏幕的
机器上就变得黑丑，全部被拉伸了。碎片的目的就是要充分合理的使用屏幕空间。
想象一下一个屏幕上左右两边各一个活动，点左边触动右边，是一件很爽的事儿哎。

概念图：

在布局文件中我们使用来添加碎片，一个碎片就相当一有一个布局文件和一个继承了
Frament(重写onCreate方法)，添加碎片到布局当中有两种方式，一种是静态添加(通过属性name="继承了Frame的类")
另外一种是通过活动Activity动态添加碎片。

例子:静态添加：

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

LeftFragment.classpackage com.example.ldp.com.fragmenttest;import android.os.Bundle;import android.support.annotation.Nullable;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;/** * Created by Administrator on 2017/3/7. */public class LeftFragment extends Fragment {    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.left_fragment,container,false);        return view;    }}

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

RightFragment.classpackage com.example.ldp.com.fragmenttest;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;/** * Created by Administrator on 2017/3/7. */public class RightFragment extends Fragment {    @Override    public View onCreateView(LayoutInflater inflater,  ViewGroup container,  Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.right_fragment,container,false);        return view;    }}

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

MainActivity这个活动不动

效果图：

动态添加：
其他文件不动修改activity_main.xml

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

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

AnotherRightFragment.classpackage com.example.ldp.com.fragmenttest;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;/** * Created by Administrator on 2017/3/7. */public class AnotherRightFragment extends Fragment {    @Override    public View onCreateView(LayoutInflater inflater,  ViewGroup container,  Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.another_right_fragment,container,false);        return view;    }}

修改MainActivity.class

package com.example.ldp.com.fragmenttest;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentTransaction;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;public class MainActivity extends AppCompatActivity implements View.OnClickListener{    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button button = (Button) findViewById(R.id.button);        button.setOnClickListener(this);//当前监听，已经通过实现onclickLister接口了    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.button:                replaceFragment(new AnotherRightFragment());                break;            default:                break;        }    }    //最关键的方法就是使用replace()方法传入容器ID和碎片实例，提交事务    private void replaceFragment(Fragment fragment){        FragmentManager fragmentManager = getSupportFragmentManager();        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();        fragmentTransaction.replace(R.id.another_right_fragment,fragment);        /**         * 按下Back键返回到上一个碎片，如果没有这句代码，将直接退出程序         * */        fragmentTransaction.addToBackStack(null);        /**         * 在开发过程很重要         * */        fragmentTransaction.commit();    }}

效果图:

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