小编use*_*414的帖子

我学习的Android与http://developer.android.com/index.html,但是当我到达http://developer.android.com/training/basics/firstapp/starting-activity.html显示信息部分,点6我有一个错误

android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.RelativeLayout 

我像教程一样一步一步地做了一切.那为什么它不起作用？

DisplayMessageActivity.java

    package com.example.flover.hellloworld;

    import android.content.Intent;
    import android.os.Bundle;
    import android.support.v7.app.AppCompatActivity;
    import android.view.Menu;
    import android.view.MenuItem; 
    import android.widget.RelativeLayout;
    import android.widget.TextView;

    public class DisplayMessageActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_message);


        Intent intent = getIntent();
        String message = intent.getStringExtra(MyActivity.EXTRA_MESSAGE);
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        RelativeLayout layout = (RelativeLayout) findViewById(R.id.content);
        layout.addView(textView);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the …