四大组建-Activity

1.Activity的跳转

显示跳转

方法一：

Intent intent=new Intent(MainActivity.this, SecondActivity.class);
startActivity(intent);

方法二：

Intent intent2=new  Intent();
intent2.setClass(本类，另外将要跳转的类);    (intent2.setClass(MainActivity.this,SecondActivity.class);)
startActivity（intent2）;

方法三：

Intent intent2=new  Intent();
intent2.setClassName（this，“将要跳转界面的名字”）；
startActivity（intent2）;

方法四：

Intent intent2=new  Intent();
intent2.setComponent(new ComponentName(MainActivity.this, OtherActivity.class));
startActivity（intent2）;

隐式跳转

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button bt = (Button) findViewById(R.id.bt);
        bt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent("Zyptest");
                startActivity(intent);
            }
        });
    }
}

更多隐式跳转

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button bt = (Button) findViewById(R.id.bt);
        bt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(Intent.ACTION_VIEW);
                intent.setData(Uri.parse("http:www.baidu.com"));
                startActivity(intent);
            }
        });
    }
}

Activity回调

三：跳转到另一个Activity后，当返回时能返回数据
1.在跳转的Activity端，调用startActivityForResult(intent2, 2),跳转到下一个Activity，其中第一个参数为传入的意图对象，第二个为设置的请求码；
2.跳转到第二个Activity后，调用setResult(10, intent)方法可返回上一个Activity，其中第一个参数为结果码，第二个为传入的意图对象；
3.在第一个Activity通过onActivityResult()方法获得返回的数据。

public class MainActivity extends AppCompatActivity {
    private int requestCode = 100;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button bt = (Button) findViewById(R.id.bt);
        bt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                startActivityForResult(intent,requestCode);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == 100 && resultCode == 4){
           String nihao = data.getStringExtra("nihao");
            Log.v("MainActivity", nihao);
        }
    }
}

public class SecondActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        Button bt2 = (Button) findViewById(R.id.bt2);
        bt2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent=new Intent();
                intent.putExtra("nihao", "我是SecondActivity");
                setResult(4,intent);
                finish();
            }
        });
    }
}