java - 如何在 android studio 中导入 android.support.v7.app.Appcompatactivity？

问题描述

我是编码新手。我对 mainactivity.java 使用了这个 import android.support.v7.app.Appcompatactivity 但我收到了一个红色错误：

无法解析符号 v7

我也确实使缓存重新启动无效，但这不起作用。如果我在没有该行的情况下运行此代码，我的应用程序可以在 Android 5.1.1 上运行，但不能在 Galaxy j6 上运行那行是做什么用的？

我的 android studio 版本是 3.5.0.21，我也可以在屏幕截图中显示我的错误以获取更多详细信息：

package com.example.bmi;

import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import android.support.v7.app.Appcompatactivity

public class MainActivity extends AppCompatActivity {

    private EditText height;
    private EditText weight;
    private TextView result;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        height = (EditText) findViewById(R.id.height);
        weight = (EditText) findViewById(R.id.weight);
        result = (TextView) findViewById(R.id.result);
    }

    public void calculateBMI(View v) {
        String heightStr = height.getText().toString();
        String weightStr = weight.getText().toString();

        if (heightStr != null && !"".equals(heightStr)
                && weightStr != null  &&  !"".equals(weightStr)) {
            float heightValue = Float.parseFloat(heightStr) / 100;
            float weightValue = Float.parseFloat(weightStr);

            float bmi = weightValue / (heightValue * heightValue);

            displayBMI(bmi);
        }
    }

    private void displayBMI(float bmi) {
        String bmiLabel = "";

        if (Float.compare(bmi, 15f) <= 0) {
            bmiLabel = getString(R.string.very_severely_underweight);
        } else if (Float.compare(bmi,  15f) > 0  &&  Float.compare(bmi, 16f) <= 0) {
            bmiLabel = getString(R.string.severely_underweight);
        } else if (Float.compare(bmi, 16f) > 0  &&  Float.compare(bmi, 18.5f) <= 0) {
            bmiLabel = getString(R.string.underweight);
        } else if (Float.compare(bmi, 18.5f) > 0  &&  Float.compare(bmi, 25f) <= 0) {
            bmiLabel = getString(R.string.normal);
        } else if (Float.compare(bmi, 25f) > 0  &&  Float.compare(bmi, 30f) <= 0) {
            bmiLabel = getString(R.string.overweight);
        } else if (Float.compare(bmi, 30f) > 0  &&  Float.compare(bmi, 35f) <= 0) {
            bmiLabel = getString(R.string.obese_class_i);
        } else if (Float.compare(bmi, 35f) > 0  &&  Float.compare(bmi, 40f) <= 0) {
            bmiLabel = getString(R.string.obese_class_ii);
        } else {
            bmiLabel = getString(R.string.obese_class_iii);
        }

        bmiLabel = bmi + "\n\n" + bmiLabel;
        result.setText(bmiLabel);
    }
}

我的 build.gradle 代码是

apply plugin: 'com.android.application'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.example.bmi"
        minSdkVersion 15
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    implementation 'androidx.recyclerview:recyclerview:1.0.0'
    //noinspection GradlePath
    implementation files('SdkManager\\extras\\android\\support\\v7\\appcompat\\libs and select android-support-v7-appcompat')
}

标签： javaandroid-studiosymbolsappcompatactivity

java - 如何在 android studio 中导入 android.support.v7.app.Appcompatactivity？

问题描述

解决方案

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