1. Pass simple data
2. Pass the data package Bundle
3. Passing value objects
4. Get the return parameters of the Activity
1. Pass simple data
How to pass simple data when Activity jumps.
The idea of passing data when starting an activity is very simple. Intent provides a series of overloads of the putExtra() method, which can temporarily store the data we want to pass in the Intent. After starting another activity, we only need to put these data It can be removed from the Intent again.
Add a Button in activity_main.xml and change the layout to LinearLayout
New hello.xml
Put a TextView inside that doesn't display anything
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""
android:id="@+id/textView_1" />
MainActivity.java
The putExtra() method receives two parameters, the first parameter is the key, which is used to retrieve the value from the Intent later, and the second parameter is the actual data to be passed.
public class MainActivity extends AppCompatActivity {
//declare variable
private Button button_1;
@Override
protected void onCreate(Bundle savedInstanceState) {
//Save the state of the Activity
super.onCreate (savedInstanceState);
setContentView(R.layout.activity_main);
// get object reference
button_1=(Button)this.findViewById(R.id.button_1);
//Register listener, anonymous inner class
button_1.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
Intent intent=new Intent(MainActivity.this,hello.class);
intent.putExtra("data","Hello jikexueyuan");//Pass string
startActivity(intent);
}
});
}
}
Here to create a new hello.java
The Intent used to start hello is obtained through the getIntent() method, and then the getStringExtra() method is called, and the corresponding key value is passed in, and the passed data can be obtained. Here, since we are passing a string, we use the getStringExtra() method to get the passed data, if the passed integer data, use the getIntExtra() method, and if the passed Boolean data, use getBooleanExtra() method, and so on.
public class hello extends AppCompatActivity {
private TextView textView_1;
protected void onCreate(Bundle savedInstanceState){
super.onCreate (savedInstanceState);
setContentView(R.layout.hello);
textView_1=(TextView)findViewById(R.id.textView_1);
Intent intent=getIntent();
textView_1.setText(intent.getStringExtra("data"));
}
}
AndroidManifest.xml
<activity
android:name="hello"
android:label="@string/app_name">
</activity>
running result:
When button 1 is clicked:
2. Pass the data package Bundle
How to pass complex data when Activity jumps.
MainActivity.java
public class MainActivity extends AppCompatActivity {
//declare variable
private Button button_2;
@Override
protected void onCreate(Bundle savedInstanceState) {
//Save the state of the Activity
super.onCreate (savedInstanceState);
setContentView(R.layout.activity_main);
// get object reference
button_2=(Button)this.findViewById(R.id.button_2);
//Register listener, anonymous inner class
button_2.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
Intent intent=new Intent(MainActivity.this,new_main.class);
Bundle bundle=new Bundle();
bundle.putString("name","jikexueyuan");//Pass string
bundle.putInt("age",2);//Pass integer type parameters
bundle.putString("name1","iwen");
intent.putExtras(bundle);
startActivity(intent);
}
});
}
}
new_main.java
public class new_main extends AppCompatActivity {
private TextView textView_2;
protected void onCreate(Bundle savedInstanceState){
super.onCreate (savedInstanceState);
setContentView(R.layout.new_main);
textView_2=(TextView)findViewById(R.id.textView_2);
Intent intent=getIntent();
Bundle data=intent.getExtras();
textView_2.setText(String.format("name=%s,age=%d，name1=%s",data.getString("name"),
data.getInt("age"), data.getString("name1", "leo")));//If name1 is not passed in, the default value leo is displayed
}
}
Another way:
MainActivity.java
public class MainActivity extends AppCompatActivity {
//declare variable
private Button button_2;
@Override
protected void onCreate(Bundle savedInstanceState) {
//Save the state of the Activity
super.onCreate (savedInstanceState);
setContentView(R.layout.activity_main);
// get object reference
button_2=(Button)this.findViewById(R.id.button_2);
//Register listener, anonymous inner class
button_2.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
Intent intent=new Intent(MainActivity.this,new_main.class);
Bundle bundle=new Bundle();
bundle.putString("name","jikexueyuan");
bundle.putInt("age",2);
bundle.putString("name1","iwen");
//intent.putExtras(bundle);
intent.putExtra("data",bundle);
startActivity(intent);
}
});
}
}
new_main.java
public class new_main extends AppCompatActivity {
private TextView textView_2;
protected void onCreate(Bundle savedInstanceState){
super.onCreate (savedInstanceState);
setContentView(R.layout.new_main);
textView_2=(TextView)findViewById(R.id.textView_2);
Intent intent=getIntent();
//Bundle data=intent.getExtras();
Bundle data=intent.getBundleExtra("data");
textView_2.setText(String.format("name=%s,age=%d，name1=%s",data.getString("name"),data.getInt("age"),data.getString("name1","leo")));
}
}
3. Passing value objects
How to pass a custom value object when Activity jumps.
Add a new button_3 in activity_main
New User.class
public class User implements Serializable{
private String name;
private int age;
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 User(String name,int age){
this.name=name;
this.age=age;
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity {
//declare variable
private Button button_3;
@Override
protected void onCreate(Bundle savedInstanceState) {
//Save the state of the Activity
super.onCreate (savedInstanceState);
setContentView(R.layout.activity_main);
// get object reference
button_3=(Button) this.findViewById(R.id.button_3);
//Register listener, anonymous inner class
button_3.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
Intent intent=new Intent(MainActivity.this,ding.class);
intent.putExtra("user",new User("jikexueyuan",2));
startActivity(intent);
}
});
}
}
ding.java
public class ding extends AppCompatActivity{
private TextView textView_3;
protected void onCreate(Bundle savedInstanceState){
super.onCreate (savedInstanceState);
setContentView(R.layout.ding);
textView_3=(TextView)findViewById(R.id.textView_3);
Intent intent=getIntent();
User user=(User)intent.getSerializableExtra("user");
textView_3.setText(String.format("User info(name=%s,age=%d)",user.getName(),user.getAge()));
}
}
Another implementation method provided by the android platform
User.java
public class User implements Parcelable{
private String name;
private int age;
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 User(String name,int age){
this.name=name;
this.age=age;
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(getName());
dest.writeInt (getAge ());
}
public static final Creator<User> CREATOR=new Creator<User>() {
@Override
public User createFromParcel(Parcel source) {
return new User(source.readString(),source.readInt());
}
@Override
public User[] newArray(int size) {
return new User[size];
}
};
}
ding.java
public class ding extends AppCompatActivity{
private TextView textView_3;
protected void onCreate(Bundle savedInstanceState){
super.onCreate (savedInstanceState);
setContentView(R.layout.ding);
textView_3=(TextView)findViewById(R.id.textView_3);
Intent intent=getIntent();
//User user=(User)intent.getSerializableExtra("user");
User user=intent.getParcelableExtra("user");
textView_3.setText(String.format("User info(name=%s,age=%d)",user.getName(),user.getAge()));
}
}