Android之startActivity和startActiv

• startActivity(intent)：只是从当前活动界面跳转到另外一个界面，两个界面中不再有联系。
• startActivityForResult(intnet,requestcode):可以经当前活动界面认为是一个父窗体，要跳转的界面为子窗体，当子窗体关闭时，父窗体会执行onActivityResult()方法，并可以获取子窗体的返回值.

以startActivityForResult为例:

MainActivity:

package com.example.tiaozhuantest01;

import android.content.Intent;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tv_text;
    private Button btn_jump;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv_text=findViewById(R.id.tv_text);
        btn_jump=findViewById(R.id.btn_jump);
        btn_jump.setOnClickListener(this);
    }
    @Override
    public void onClick(View v) {
        if(v.getId()==R.id.btn_jump){
            Intent intent = new Intent();
            intent.setClass(this,SettingActivity.class);
            startActivityForResult(intent,0);
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode==0){
            if(resultCode==0){
                Bundle mBundle=data.getExtras();
                if(mBundle!=null)
                    tv_text.setText("回传的信息为："+mBundle.getString("send"));
            }
        }
    }
}

SettingActivity:

package com.example.tiaozhuantest01;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class SettingActivity extends AppCompatActivity implements View.OnClickListener {
    private Button btn_back;
    private EditText et_text;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_setting);
        btn_back=findViewById(R.id.btn_back);
        btn_back.setOnClickListener(this);
        et_text=findViewById(R.id.et_text);
    }
    @Override
    public void onClick(View v) {
        if(v.getId()==R.id.btn_back){
            Intent intent = new Intent();
            intent.putExtra("send",et_text.getText().toString());
            setResult(0,intent);
            finish();
        }
    }
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <View
        android:layout_width="match_parent"
        android:layout_height="200dp"></View>
   <TextView
       android:id="@+id/tv_text"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_gravity="center"
       android:text="回传的信息为："
       android:textSize="25sp"/>
    <Button
        android:id="@+id/btn_jump"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="跳转"/>
</LinearLayout>

activity_setting:

<?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="match_parent"
    android:orientation="vertical">

    <View
        android:layout_width="match_parent"
        android:layout_height="200dp"></View>

    <EditText
        android:id="@+id/et_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:hint="输入文字"/>

    <Button
        android:id="@+id/btn_back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="返回"
        android:layout_gravity="center"/>
</LinearLayout>

效果图如下：

image.png
image.png
image.png

总结:

• 调用startActivityForResult方法可以让跳转的目的Activity实现onActivityResult方法。
• 调用startActivity方法只是普通的跳转。