先记下要点

跳转

    button1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(FirstActivity.this,SecondActivity.class);
            startActivity(intent);
        }
    });

传递数据

firstactivity发送数据

    button1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(FirstActivity.this,SecondActivity.class);
            String data = "hello second";
            intent.putExtra("extra_data", data);
            startActivity(intent);
        }
    });

secondactivity接收数据

    Intent intent = getIntent();
    String data = intent.getStringExtra("extra_data");

返回数据

跳转前的代码

    button1.setOnClickListener(new View.OnClickListener() {
        @Override
//重写 onActivityResult
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    switch (requestCode) {
        case 1:
            if (resultCode == RESULT_OK) {
                String returnedData = data.getStringExtra("data_return");
                Log.d("FirstActivity", returnedData);
            }
            break;
        default:
    }
}
        public void onClick(View v) {
            Intent intent = new Intent(FirstActivity.this,SecondActivity.class);
            String data = "hello second";
            intent.putExtra("extra_data", data);
            //startActivity(intent);
          startActivityForResult(intent, 1);
        }
    });

    Intent intent = getIntent();
    String data = intent.getStringExtra("extra_data");

跳转的代码

@Override
public void onBackPressed(){
    Intent intent = new Intent();
    intent.putExtra("data_return","hello first");
    setResult(RESULT_OK, intent);
    finish();
}