Intent如何传递List？
答：需要首先将要传递的对象实体类进行序列化。再通过Intent、Bundle对象传递给其他Activity。
Why? 不同 Activity 之间传输数据可以通过 Intent 对象的 putExtra 方法传递，对于 java 的八大基本数据类型(char int float double long short boolean byte)传递是没有问题的，但是如果传递比较复杂的对象类型（比如对象，比如集合等），那么就可能存在问题，就需要实现数据对象的数据序列化, 将这些对象放到一个 Intent 或者 Bundle 里面，然后再传递。
如何对实体类进行序列化？
Android中实现序列化有两种机制（实现Serializable接口/实现parcelable接口），我们采用第二种机制：实现parcelable接口。
- 打开AndroidStudio的设置界面，搜索Parcelable安装序列化插件
- 对对象实体类进行改造：需要实现Parcelable接口（此时提示需要重写几个方法，不用管，采用插件进行第三步处理自动重写）
- 右键选择Parcelable插件，一键重写方法，得到：用法中的步骤四。
效果预览
用法
步骤一、创建ActivityA的布局文件
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".blog2.Case68"
tools:ignore="MissingConstraints">
<TextView
android:layout_width="match_parent"
android:layout_height="40dp"
android:background="@color/black"
android:gravity="center"
android:text="Activity_A"
android:textColor="@color/white"
android:textSize="20sp" />
<Button
android:id="@+id/btnGo"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="跳转页面传值"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
android:padding="15dp"
android:textSize="20sp" />
</androidx.constraintlayout.widget.ConstraintLayout>
步骤二、创建实体类：Movie
/**
* @data on 12/2/20 9:33 AM
* @auther armStrong
* @describe 电影实体类
*/
public class Movie{
private int id;
private String name;
private String record; //票房记录
public Movie() {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getRecord() {
return record;
}
public void setRecord(String record) {
this.record = record;
}
public Movie(int id, String name, String record) {
this.id = id;
this.name = name;
this.record = record;
}
}
步骤三、在ActivityA中书写业务逻辑代码
public class Case68 extends AppCompatActivity {
private Button btnA;
//定义一个ArrayList并且跳转时传递它
private ArrayList movieList = new ArrayList<Movie> ();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_case68);
initView();
initList();
btnA.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
goToB();
}
});
}
private void initView() {
btnA = findViewById(R.id.btnGo);
}
private void goToB(){
Intent intent = new Intent();
intent.putExtra("key1", "可可托海的牧羊人");
intent.putParcelableArrayListExtra("key2",movieList);
intent.setClass(this, Case68Other.class);
startActivity(intent);
finish();
}
private void initList(){
movieList.add(new Movie(1,"《金刚川》","100万"));
movieList.add(new Movie(2,"《疯狂原始人》","200万"));
movieList.add(new Movie(3,"《一秒钟》","300万"));
movieList.add(new Movie(4,"《除暴》","400万"));
}
}
步骤四、对实体类Movie进行序列化（对比第二步）
/**
* @data on 12/2/20 9:33 AM
* @auther armStrong
* @describe 电影实体类——序列化
*/
public class Movie implements Parcelable {
private int id;
private String name;
private String record; //票房记录
public Movie() {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getRecord() {
return record;
}
public void setRecord(String record) {
this.record = record;
}
public Movie(int id, String name, String record) {
this.id = id;
this.name = name;
this.record = record;
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(this.id);
dest.writeString(this.name);
dest.writeString(this.record);
}
protected Movie(Parcel in) {
this.id = in.readInt();
this.name = in.readString();
this.record = in.readString();
}
public static final Creator<Movie> CREATOR = new Creator<Movie>() {
@Override
public Movie createFromParcel(Parcel source) {
return new Movie(source);
}
@Override
public Movie[] newArray(int size) {
return new Movie[size];
}
};
}
步骤五、创建ActivityB的布局文件
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".activity.Case68Other"
android:background="@color/gray"
tools:ignore="MissingConstraints">
<TextView
android:layout_width="match_parent"
android:layout_height="40dp"
android:background="@color/black"
android:gravity="center"
android:text="Activity_B"
android:textColor="@color/white"
android:textSize="20sp" />
<TextView
android:id="@+id/showTvStr"
android:layout_width="match_parent"
android:layout_height="100dp"
android:gravity="center"
android:textSize="18sp"
android:background="@color/white"
android:text="输出字符串"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<View
android:id="@+id/divider"
android:layout_width="0dp"
android:layout_marginHorizontal="10dp"
android:layout_height="1dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
android:background="@color/black"
app:layout_constraintTop_toBottomOf="@id/showTvStr" />
<TextView
android:id="@+id/showTvList"
android:background="@color/white"
android:layout_width="match_parent"
android:layout_height="300dp"
android:gravity="center"
android:textSize="18sp"
android:text="输出列表数据"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@id/divider" />
</androidx.constraintlayout.widget.ConstraintLayout>
步骤六、在ActivityB中书写业务逻辑代码
public class Case68Other extends AppCompatActivity {
private TextView tvShowStr;
private TextView tvShowList;
private String str;
private ArrayList<Movie> mList = new ArrayList<Movie> ();;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_case68_other);
initView();
getParameter();
showText();
}
private void initView() {
tvShowStr = findViewById(R.id.showTvStr);
tvShowList = findViewById(R.id.showTvList);
}
private void getParameter(){
str = getIntent().getStringExtra("key1");
mList = getIntent().getParcelableArrayListExtra("key2");
}
private void showText(){
tvShowStr.setText(str);
StringBuilder stringBuilder = new StringBuilder();
for (Movie m : mList){
stringBuilder.append("Id:"+m.getId()+";"+"Name:"+m.getName()+";"+"Record:"+m.getRecord()+"."+"\n");
}
tvShowList.setText(stringBuilder);
}
}
大功告成！
网友评论