ios如何快速转型安卓开发-专题2

1.活动的生命周期

1.返回栈

安卓通过返回栈对活动进行管理，按下Back或者执行finish方法时，栈顶的活动销毁。

2.活动状态

（1）运行状态：栈顶。
（2）暂停状态：不处于栈顶，但仍然可见。
（3）停止状态：不处于栈顶，不可见。
（4）销毁状态：从返回栈移除

3.活动的生存期

（1）onCreate：活动第一次创建的时候调用
（2）onStart：活动由不可见变为可见
（3）onResume：活动准备好和用户交互时调用
（4）onPause：系统准备去启动或者恢复另一个活动的时候调用。通常会在这个方法中将一些消耗CPU的资源释放，保存一些关键数据，执行速度一定要快，否则会影响到栈顶活动的使用。
（5）onStop：活动完全不可见的时候调用。与onPause方法的主要区别在于，如果启动的新活动是一个对话框式的活动，onPause会执行，而onStop不会执行
（6）onDestory：活动销毁之前调用
（7）onRestart：活动由停止状态变成运行状态之前调用，也就是活动被重新启动了。
完整生存期：onCreate 到onDestroy之间。
可见生存期：onStart和onStop之间，处于可见。
前台生存期：onResume和onPause之间，处于运行形态。
Activity中提供了一个onSaveInstanceState（）回调方法，保证活动在回收之前一定会被调，通过这个方法可以解决活动被回收时临时数据得不到保存的情况。
onSaveInstanceState（）会提供一个Bundle类型的参数，提供了一系列的方法用于保存数据。
保存的数据可以在onCreate上的Bundle参数取对应的保存信息。Intent可以结合Bundle一起用于传输局，可以吧传递的数据保存在Bundle对象中，然后将Bundle对象放在Intent中，到了目标活动之后再取出对应的Bundle。

4.活动的启动模式

给activity标签指定android：launchMode属性来选择启动模式。
（1）standard：活动默认启动模式。启动后位于返回栈顶。
（2）singleTop：如果返回栈顶已经是该活动，直接使用它，不会创建新的活动，该活动没有处于栈顶还是会创建多个活动
（3）singleTask：返回栈是否存在该活动，存在直接使用，将所有位于该活动之上的出栈。
（4）singleInstance：启用一个新的返回栈来管理这个活动
实际用法：修改活动的继承方式，输出当前类名，可以快速定位当前类。创建活动管理器，通过List管理活动，通过finishAll，将所有Activity销毁。继承活动，将对应的启动函数hook掉，可以解决传数据的问题，而不用阅读对应的代码。

2.UI基本控件

1.TextView

android🆔控件标识符
match_parent/fill_parent：控件大小和父布局一样
wrap_parent：与当前的内容大小一致
gravity：文字对齐方式
textSize：文字大小
textColor：文字颜色

2.button

textAlllCaps：文字全大写
setOnClickListener:添加点击事件 实现接口/实现匿名类

3.EditText

hint：提示文本
maxLines：最大行数
findViewById：获取实例

4.ImageView

src:资源路径
setImageResource：设置图片

5.ProgressBar

progressBar.getVisibility() == View.GONE
style="?android:attr/progressBarStyleHorizontal"
android:max="100"
int progress = progressBar.getProgress();
progress = progress + 10;
progressBar.setProgress(progress);

6.AlertDialog

点击查看代码

        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() {
          @Override
          public void onClick(DialogInterface dialog, int which) {

          }
        });
        dialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
          @Override
          public void onClick(DialogInterface dialog, int which) {

          }
        });
        dialog.show();

7.ProgressDialog

点击查看代码

        ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
        progressDialog.setTitle("This is ProgressDialog");
        progressDialog.setMessage("Loading ...");
        progressDialog.setCancelable(true);
        progressDialog.show();

3.UI基本布局

1.线性布局

将所包含空间由上到下一次排列
layout_gravity属性，对齐方式
layout_weight，按比例方式指定控件大小，所有控件权重值相加，按比例值分配大小
orientation：设置线性布局方向

2.相对布局

layout_alignParentLeft左对齐...centerInParent中间，每个空间相对于父布局进行对齐。
layout_toRightOf：表示让一个控件位于另一个控件的右侧。

3.帧布局

所有空间都会摆放在布局的左上角

4.百分比布局

在dependencies闭包添加 compile ' 待确认

5.约束布局

可以按照比例约束调整空间位置和大小，更好适配机型

点击查看代码

android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="5dp"
    android:text="Back"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    android:layout_marginLeft="0dp"

6.自定义布局

创建TitleLayout继承自LinearLayout，重写TitleLayout控件的构造函数，对于布局进行动态加载，需要借助LayoutInflater

4.ListView

点击查看代码

public class MainActivity extends AppCompatActivity {
  private String[] data = {"Apple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple", "Couple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple", "Couple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple"};
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>( MainActivity.this, android.R.layout.simple_list_item_1, data);
    ListView listView = (ListView) findViewById(R.id.list_view);
    listView.setAdapter(adapter);
  }
}

1.定制ListView的界面

点击查看代码

public class FruitAdapter extends ArrayAdapter<Fruit> {

  private  int resourceId;

  public FruitAdapter(@NonNull Context context, int resource,
      @NonNull List<Fruit> objects) {
    super(context, resource, objects);
    resourceId = resource;
  }

  public View getView(int position, View convertView, ViewGroup praent) {
    Fruit fruit = getItem(position);
    View view = LayoutInflater.from(getContext()).inflate(resourceId, praent, false);
    TextView textView1 = (TextView) view.findViewById(R.id.left_text);
    TextView textView2 = (TextView) view.findViewById(R.id.right_text);
    textView1.setText(fruit.getName());
    textView2.setText(fruit.getDetail());
    return view;
  }
}
	public class Fruit {
  private String name;
  private String detail;
  public Fruit (String name, String detail) {
    this.name = name;
    this.detail = detail;
  }

  public String getName() {
    return name;
  }

  public String getDetail() {
    return detail;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    Fruit fruit = (Fruit) o;
    return Objects.equals(name, fruit.name) &&
        Objects.equals(detail, fruit.detail);
  }

  @Override
  public int hashCode() {
    return Objects.hash(name, detail);
  }
}

private List<Fruit> fruitList = new ArrayList<>();
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initFruits();
    FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.item_layout ,fruitList);
    ListView listView = (ListView) findViewById(R.id.list_view);
    listView.setAdapter(adapter);
  }
  private void initFruits () {
    for (int i=0; i < 2; i++) {
      Fruit apple = new Fruit("Apple", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple1", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple2", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple3", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple4", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple4", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);

    }

提升ListView的运行效率：类似于oc的复用机制，判断View是否创建，创建了直接使用，否则创建新的。

方式1:

点击查看代码

 public View getView(int position, View convertView, ViewGroup praent) {
    Fruit fruit = getItem(position);
    View view;
    if (convertView == null) {
      view = LayoutInflater.from(getContext()).inflate(resourceId, praent, false);
    } else {
      view = convertView;
    }
}

方式二：

点击查看代码

public View getView(int position, View convertView, ViewGroup praent) {
    Fruit fruit = getItem(position);
    View view;
    ViewHolder viewHolder;
    if (convertView == null) {
      view = LayoutInflater.from(getContext()).inflate(resourceId, praent, false);
      viewHolder = new ViewHolder();
      viewHolder.left = (TextView) view.findViewById(R.id.left_text);
      viewHolder.right = (TextView) view.findViewById(R.id.right_text);
      view.setTag(viewHolder);
    } else {
      view = convertView;
      viewHolder = (ViewHolder)view.getTag();
    }
    viewHolder.left.setText(fruit.getName());
    viewHolder.left.setText(fruit.getName());
    //TextView textView1 = (TextView) view.findViewById(R.id.left_text);
    //TextView textView2 = (TextView) view.findViewById(R.id.right_text);
    //textView1.setText(fruit.getName());
    //textView2.setText(fruit.getDetail());
    return view;
  }

  class ViewHolder {
    TextView left;
    TextView right;
  }

2.设置点击事件

点击查看代码

 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();
      }
    });

5.RecycleView

点击查看代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="wrap_content">
  <TextView
    android:id="@+id/left_text"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>
  <TextView
    android:id="@+id/right_text"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center_vertical"
    android:layout_marginStart="10dp"/>

</LinearLayout>
	
	<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context=".MainActivity"
  android:orientation="horizontal">
  <androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recycleview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

  <ListView
    android:id="@+id/list_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:layout_editor_absoluteX="0dp"
    tools:layout_editor_absoluteY="0dp" />

  <TextView
    android:id="@+id/text_view"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

</LinearLayout>
	
	package com.example.listviewtest;

import java.util.ArrayList;
import java.util.List;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.app.Fragment;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
  private String[] data = {"Apple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple", "Couple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple", "Couple", "Banana", "Couple", "Banana", "Couple", "Banana", "Couple"};
  private List<Fruit> fruitList = new ArrayList<>();
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initFruits();
    /*FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.item_layout ,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();
      }
    });*/
    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycleview);
    LinearLayoutManager layoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(layoutManager);
    FruitsAdapter adapter = new FruitsAdapter(fruitList);
    recyclerView.setAdapter(adapter);

  }
  private void initFruits () {
    for (int i=0; i < 2; i++) {
      Fruit apple = new Fruit("Apple", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple1", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple2", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple3", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple4", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple4", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);
      apple = new Fruit("Apple5", "Juice");
      fruitList.add(apple);

    }

  }
}

package com.example.listviewtest;

import java.util.List;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

public class FruitsAdapter extends RecyclerView.Adapter<FruitsAdapter.ViewHolder> {
  private List<Fruit> mFruitList;

  public FruitsAdapter(List<Fruit> fruitList) {
    mFruitList = fruitList;
  }

  @NonNull
  @Override
  public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_layout,parent,false);
    ViewHolder holder = new ViewHolder(view);
    return holder;
  }

  @Override
  public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
    Fruit fruit = mFruitList.get(position);
    holder.left.setText(fruit.getName());
    holder.right.setText(fruit.getDetail());
  }

  @Override
  public int getItemCount() {
    return mFruitList.size();
  }

  static class ViewHolder extends RecyclerView.ViewHolder {
    TextView left;
    TextView right;
    public ViewHolder(View view) {
      super(view);
      left = (TextView) view.findViewById(R.id.left_text);
      right = (TextView) view.findViewById(R.id.right_text);
    }
  }
}

设置水平滚动

点击查看代码

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycleview);
    LinearLayoutManager layoutManager = new LinearLayoutManager(this);
    layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
    recyclerView.setLayoutManager(layoutManager);
    FruitsAdapter adapter = new FruitsAdapter(fruitList);
    recyclerView.setAdapter(adapter);

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="100dp"
  android:layout_height="wrap_content">
  <TextView
    android:id="@+id/left_text"
    android:layout_width="wrap_content"
    android:layout_gravity="center_horizontal"
    android:layout_height="wrap_content"/>
  <TextView
    android:id="@+id/right_text"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal"
    android:layout_marginStart="10dp"/>

</LinearLayout>

瀑布流

点击查看代码

    StaggeredGridLayoutManager layoutManager = new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="match_parent"
  android:layout_margin="5dp"
  android:layout_height="wrap_content">
  <TextView
    android:id="@+id/left_text"
    android:layout_width="wrap_content"
    android:layout_gravity="center_horizontal"
    android:layout_height="wrap_content"/>
  <TextView
    android:id="@+id/right_text"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="left"
    android:layout_marginStart="10dp"/>

</LinearLayout>

设置点击事件

点击查看代码

public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_layout,parent,false);
    ViewHolder holder = new ViewHolder(view);
    holder.left.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        int position = holder.getAdapterPosition();
        Toast.makeText(v.getContext(), "you clicked title"+position, Toast.LENGTH_SHORT).show();
      }
    });
    holder.right.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        int position = holder.getAdapterPosition();
        Toast.makeText(v.getContext(), "you clicked detail"+position, Toast.LENGTH_SHORT).show();
      }
    });
    return holder;
  }