android-----实现不两个不同的activity的跳转和数据传递

　最近学习了android的界面的跳转，一个是activity和fragment之间的跳转（之前的博客说过），一个是不同activity之间的跳转。

　　　　activity直接的跳转很简单，只需要用Intent即可，而且传递数据很简便，如果只是传递简单数据，即可直接使用,如果传递复杂的数据，比如一个类，就得需要把类定义为。

　　　　个人觉得android跳转页面要比JAVA的简单的很多！！。看例子。

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　　下图是从一个Activity跳转到另一个activity，并将数据传递过去。

　  　   

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　　实体类：（因为我们要传递一个实体类，所有要用到Parcelable）

　　Android中的Activity传递数据时，为了方便往往将很多数据封装成对象，然后将整个对象传递过去。传对象的时候有两种情况，一种是实现Parcelable接口，一种是实现Serializable接口。

　　先将Grade implements Parcelable，然后点击Grade，会出现一个红色的小灯泡，点击即可，生成的函数不需要动，位置也不要动，否则会保出错。

package com.example.testparcelable;

import android.os.Parcel;
import android.os.Parcelable;

public class Student implements Parcelable{
    private String name;
    private int age;
    private Grade grade;

    public Student(String name, int age, Grade grade) {
        this.name = name;
        this.age = age;
        this.grade = grade;
    }

    protected Student(Parcel in) {
        name = in.readString();
        age = in.readInt();
        grade = in.readParcelable(Grade.class.getClassLoader());
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(name);
        dest.writeInt(age);
        dest.writeParcelable(grade, flags);
    }

    @Override
    public int describeContents() {
        return 0;
    }

    public static final Creator<Student> CREATOR = new Creator<Student>() {
        @Override
        public Student createFromParcel(Parcel in) {
            return new Student(in);
        }

        @Override
        public Student[] newArray(int size) {
            return new Student[size];
        }
    };

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Grade getGrade() {
        return grade;
    }

    public void setGrade(Grade grade) {
        this.grade = grade;
    }
}
class Grade implements Parcelable {
    private int math;
    private int chinese;
    private int English;

    public Grade(int math, int chinese, int english) {
        this.math = math;
        this.chinese = chinese;
        English = english;
    }

    protected Grade(Parcel in) {
        math = in.readInt();
        chinese = in.readInt();
        English = in.readInt();
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(math);
        dest.writeInt(chinese);
        dest.writeInt(English);
    }

    @Override
    public int describeContents() {
        return 0;
    }

    public static final Creator<Grade> CREATOR = new Creator<Grade>() {
        @Override
        public Grade createFromParcel(Parcel in) {
            return new Grade(in);
        }

        @Override
        public Grade[] newArray(int size) {
            return new Grade[size];
        }
    };

    public int getMath() {
        return math;
    }

    public void setMath(int math) {
        this.math = math;
    }

    public int getChinese() {
        return chinese;
    }

    public void setChinese(int chinese) {
        this.chinese = chinese;
    }

    public int getEnglish() {
        return English;
    }

    public void setEnglish(int english) {
        English = english;
    }
}

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　　MainActivity：为了操作方便我们使用dataBinding，在里android{defaultConfig{}}里设置，然后在activity_main.xml点击text，将鼠标移到该位置，点击小灯泡，如图。转换为data binding layout。这样我们就不用通过获取ID来对控件进行操作。

　　

package com.example.testparcelable;

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;

import com.example.testparcelable.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        final ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        binding.button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = binding.editTextName.getText().toString();
                int age = Integer.valueOf(binding.editTextAge.getText().toString());
                int chinese = Integer.valueOf(binding.editTextChinese.getText().toString());
                int english = Integer.valueOf(binding.editTextEnglish.getText().toString());
                int math = Integer.valueOf(binding.editTextMath.getText().toString());
                Student student = new Student(name,age,new Grade(math,chinese,english) );
                Intent intent = new Intent(MainActivity.this,Main2Activity.class);
                Bundle bundle = new Bundle();
                bundle.putParcelable("student",student);
                intent.putExtra("bundle", bundle);
                startActivity(intent);
            }
        });

    }
}

　　

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　　main2Activity:对一做同样的操作。　

package com.example.testparcelable;

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;

import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

import com.example.testparcelable.databinding.ActivityMain2Binding;
import com.example.testparcelable.databinding.ActivityMainBinding;

import org.w3c.dom.Text;

public class Main2Activity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityMain2Binding binding = DataBindingUtil.setContentView(this, R.layout.activity_main2);
        Intent intent = getIntent();
        Bundle bundle = intent.getBundleExtra("bundle");
        Student student = bundle.getParcelable("student");
        binding.textViewName.setText(student.getName());
        binding.textViewAge.setText(String.valueOf(student.getAge()));
        binding.textViewChinese.setText(String.valueOf(student.getGrade().getChinese()));
        binding.textViewEnglish.setText(String.valueOf(student.getGrade().getEnglish()));
        binding.textViewMath.setText(String.valueOf(student.getGrade().getMath()));

    }
}

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