Activity的三种跳转

一个界面跳转到另一个界面，这就Activity的跳转。我们在开发中常见的跳转有三种。普通跳转、有返回值的跳转、透传跳转。我们先来看一种。

1 . Activity的普通跳转（传值跳转）

这个跳转是最简单的

Intent intent=new Intent();

intent.setClass(this, OtherActivity.class);

intent.setClassName(this, "com.zy.MutiActivity.OtherActivity"); //方法3 此方式可用于打开其它的应用

intent.setComponent(new ComponentName(this, OtherActivity.class)); //方法4

intent.putXXX("key" , value);//传值

startActivity(intent2); //只用Activity的这个方法，因为与有返回值的跳转使用的跳转的方法是不一样的。

2 . Activity有返回值得跳转

先看代码：

发起请求的界面

public class SecondActivity extends Activity {private Button but ,but1 ;
    private TextView textView ;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);
        setContentView( R.layout.secondlayout);
        but = (Button) findViewById( R.id.but2);
        but1 = (Button) findViewById( R.id.but22);
        textView = (TextView) findViewById( R.id.text);
        but.setOnClickListener(new View.OnClickListener() {@Override
            public void onClick(View v) {Intent intent = new Intent();
                intent.setClass( SecondActivity.this , ThirdActivity.class);
                startActivityForResult(intent , 1 ); //第二参数为请求码，代表是从这个界面跳转的。
            }});
        but1.setOnClickListener(new View.OnClickListener() {@Override
            public void onClick(View v) {finish();
            }});
        System.out.println(" =======> onCreate");
    }@Override
    protected void onStart() {super.onStart();
        System.out.println(" =======> onStart");
    }@Override
    protected void onResume() {super.onResume();
        System.out.println(" =======> onResume");
    }@Override
    protected void onPause() {super.onPause();
        System.out.println(" =======> onPause");
    }@Override
    protected void onStop() {super.onStop();
        System.out.println(" =======> onStop");
    }@Override
    protected void onDestroy() {super.onDestroy();
        System.out.println(" =======> onDestroy");
    }@Override
    protected void onRestart() {super.onRestart();
        System.out.println(" =======> onRestart");
    }/**
     * 这个方法用来接收返回值
     * @param requestCode 请求码，当requestCode与上面跳转时传的请求码一样时，说明是这个界面的请求
     * @param resultCode  结果码（是否成功）
     * @param data        返回来的数据保存在这里面
     */
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);
        System.out.println("===========> onActivityResult");
        if(requestCode == 1 ){if(resultCode == Activity.RESULT_OK){textView.setText(data.getStringExtra("key"));
            }}}
}

返回结果的界面代码：

public class ThirdActivity extends Activity{private Button but , but1 ;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);
        setContentView( R.layout.thirdlayout);
        but = (Button) findViewById( R.id.but3);
        but1 = (Button) findViewById( R.id.but33);
        but.setOnClickListener(new View.OnClickListener() {@Override
            public void onClick(View v) {Intent intent = new Intent();
                intent.setClass( ThirdActivity.this , MainActivity.class);
                startActivity( intent );
            }});
        but1.setOnClickListener(new View.OnClickListener() {@Override
            public void onClick(View v) {Intent intent = new Intent();
                intent.putExtra("key" , "有返回值的跳转");
                setResult(Activity.RESULT_OK ,intent ); //Activity.RESULT_OK结果码，OK为成功 ， intent保存数据
                finish();
            }});
    }
}

看结果：

图是有点丑了，但能说明效果就可以了。

 @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);
        System.out.println("===========> onActivityResult");
        if(requestCode == 1 ){if(resultCode == Activity.RESULT_OK){textView.setText(data.getStringExtra("key"));
            }}}

方法的解析

requestCode ：这个值是通过startActivityResult( )方法传递过去的Requstcode的请求码，传递过去的是多少这个值就是多少。那么不要这个值是否可以？设想一下，假如ActivityA 界面有两个操作，一个操作是从AcitivityB获取返回的结果，另外一个操作是从ActivityC获取操作，而我们不重写onActivityResult方方法接受返回值，那么如何区分是哪个界面的返回值呢？这个时候就需要判断requestCode值，requestCode 这个值是通过startActivityResult( )方法原封不动的传递过去的，所以我们可以定义一个从B跳转的requestCode 值（假设为 1 ），设B的跳转requestCode 值（假设为 2 ）。我们就可以在A界面的onActivityResult（）方法中根据requestCode值来判断只从那个界面返回的值了，然后做不同的逻辑处理。

resultCode ：结果的状态，这个值分别为Activity.CANCE , Activtity.RESULT_OK：OK代表返回值正常，这个时候我们就可以处理结果，如果为canse说明异常这个时候获取不到数据。

data : 返回的数据就保存在这个里面，从这个里面获取数据。

05-12 17:17:30.276 23514-23514/com.example.administrator.sharedpreferences I/System.out: ===========> onActivityResult
05-12 17:17:30.276 23514-23514/com.example.administrator.sharedpreferences I/System.out: =======> onRestart
05-12 17:17:30.276 23514-23514/com.example.administrator.sharedpreferences I/System.out: =======> onStart
05-12 17:17:30.276 23514-23514/com.example.administrator.sharedpreferences I/System.out: =======> onResume

说明onActivityResult（）再onRestart（）的前面执行。需要注意

2 . Activity的透传跳转。

看代码：

MainActivity

public class MainActivity extends FragmentActivity {private boolean tager = false;
    private EditText keyET;
    private EditText valueET;
    private Button insertBtn;
    private Button deleteBtn;
    private Button modifyBtn;
    private Button queryBtn;
    private Button clearBtn;
    private Button startActivity ;
    private TextView textView;
    /** 存储的文件名 */
    public static final String DATABASE = "Database";
    /** 存储后的文件路径：/data/data/<package name>/shares_prefs + 文件名.xml */
    public static final String PATH = "/data/data/code.sharedpreferences/shared_prefs/Database.xml";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        keyET = (EditText) findViewById(R.id.key);
        valueET = (EditText) findViewById(R.id.value);
        insertBtn = (Button) findViewById(R.id.insert);
        deleteBtn = (Button) findViewById(R.id.delete);
        modifyBtn = (Button) findViewById(R.id.modify);
        queryBtn = (Button) findViewById(R.id.query);
        clearBtn = (Button) findViewById(R.id.clear);
        startActivity = (Button) findViewById( R.id.but1);
        // 用于显示存储文件中数据
        textView = (TextView) findViewById(R.id.content);
        insertBtn.setOnClickListener(new OperateOnClickListener());
        deleteBtn.setOnClickListener(new OperateOnClickListener());
        modifyBtn.setOnClickListener(new OperateOnClickListener());
        queryBtn.setOnClickListener(new OperateOnClickListener());
        clearBtn.setOnClickListener(new OperateOnClickListener());
        startActivity.setOnClickListener( new OperateOnClickListener());
    }class OperateOnClickListener implements View.OnClickListener {@Override
        public void onClick(View v) {// 获取SharedPreferences对象
            SharedPreferences sp = getSharedPreferences(DATABASE, Activity.MODE_PRIVATE);
            // 获取Editor对象
            SharedPreferences.Editor editor = sp.edit();
            // 获取界面中的信息
            String key = keyET.getText().toString();
            String value = valueET.getText().toString();
            switch (v.getId()) {// 插入数据
                case R.id.insert:if(!tager) {editor.putString("1", "123");
                        editor.commit();
                        tager = true;
                    }else{editor.putInt("1", 456);
                         editor.commit();
                        tager = false;
                }textView.setText(MainActivity.this.print());
                    break;
                // 删除数据
                case R.id.delete://editor.remove(key);
                    int value1 = Integer.valueOf(value);
                    editor.putInt(key, value1);
                    editor.commit();
                    textView.setText(MainActivity.this.print());
                    break;
                // 修改数据
                case R.id.modify:editor.putString(key, value);
                    editor.commit();
                    textView.setText(MainActivity.this.print());
                    break;
                // 查询数据
                case R.id.query:String result = sp.getString(key, "");
                    textView.setText("key=" + key + ",value=" + result);
                    break;
                // 清空所有数据
                case R.id.clear:editor.clear();
                    editor.commit();
                    textView.setText(MainActivity.this.print());
                    break;
                case R.id.but1:Intent intent = new Intent();
                    intent.setClass( MainActivity.this , SecondActivity.class);
                    startActivityForResult(intent , 100);
                    break;
            }}}/** 获取存储文件的数据 */
    private String print() {StringBuffer buff = new StringBuffer();
        try {BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(PATH)));
            String str;
            while ((str = reader.readLine()) != null) {buff.append(str + "/n");
            }} catch (Exception e) {e.printStackTrace();
        }return buff.toString();
    }@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {super.onActivityResult(requestCode, resultCode, data);
        if(requestCode  == 100 && resultCode == Activity.RESULT_OK){textView.setText(data.getStringExtra("key"));
        }}
}

SencedActivity

public class SecondActivity extends Activity {private Button but ,but1 ;
    private TextView textView ;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);
        setContentView( R.layout.secondlayout);
        but = (Button) findViewById( R.id.but2);
        but1 = (Button) findViewById( R.id.but22);
        textView = (TextView) findViewById( R.id.text);
        but.setOnClickListener(new View.OnClickListener() {@Override
            public void onClick(View v) {Intent intent = new Intent();
                intent.setClass( SecondActivity.this , ThirdActivity.class);
                intent.setFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT);
                startActivity( intent );
                finish();
            }});
        but1.setOnClickListener(new View.OnClickListener() {@Override
            public void onClick(View v) {finish();
            }});
        System.out.println(" =======> onCreate");
    }@Override
    protected void onStart() {super.onStart();
        System.out.println(" =======> onStart");
    }@Override
    protected void onResume() {super.onResume();
        System.out.println(" =======> onResume");
    }@Override
    protected void onPause() {super.onPause();
        System.out.println(" =======> onPause");
    }@Override
    protected void onStop() {super.onStop();
        System.out.println(" =======> onStop");
    }@Override
    protected void onDestroy() {super.onDestroy();
        System.out.println(" =======> onDestroy");
    }@Override
    protected void onRestart() {super.onRestart();
        System.out.println(" =======> onRestart");
    }
}

ThirdActivity

public class ThirdActivity extends Activity{private Button but , but1 ;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);
        setContentView( R.layout.thirdlayout);
        but = (Button) findViewById( R.id.but3);
        but1 = (Button) findViewById( R.id.but33);
        but.setOnClickListener(new View.OnClickListener() {@Override
            public void onClick(View v) {Intent intent = new Intent();
                intent.setClass( ThirdActivity.this , MainActivity.class);
                startActivity( intent );
            }});
        but1.setOnClickListener(new View.OnClickListener() {@Override
            public void onClick(View v) {Intent intent = new Intent();
                intent.putExtra("key" , "有返回值的跳转");
                setResult(Activity.RESULT_OK ,intent ); //Activity.RESULT_OK结果码，OK为成功 ， intent保存数据
                finish();
            }});
    }
}