Main1Activity.java

package io.github.btpka3.hi;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.CoordinatorLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.ContentFrameLayout;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.RelativeLayout;
import android.widget.TextView;

public class Main1Activity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
        Log.v("Hi", message);
        View v = this.findViewById(android.R.id.content);
        Log.v("Hi", v.toString());

        // 找到所需的可视组件,并更新文本。
        ContentFrameLayout contentFrameLayout = (ContentFrameLayout) v;
        CoordinatorLayout coordinatorLayout = (CoordinatorLayout) contentFrameLayout.getChildAt(0);
        RelativeLayout relativeLayout = (android.widget.RelativeLayout) coordinatorLayout.getChildAt(1);

        TextView textview = (TextView) relativeLayout.getChildAt(0);
        textview.setText("Hi: " + message);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}